Update dialog.md with info about filter extensions
Update dialog.md with info about filter extensions

There was some confusion about the correct way to add an `All Files` filter (see #2525), so I added it to the example.
Also added a short note about the extension syntax.

This is related to PR #2547.
jonatasfreitasv/electron,mrwizard82d1/electron,matiasinsaurralde/electron,Evercoder/electron,SufianHassan/electron,micalan/electron,beni55/electron,jaanus/electron,beni55/electron,bobwol/electron,tinydew4/electron,electron/electron,pombredanne/electron,leolujuyi/electron,jtburke/electron,kazupon/electron,kenmozi/electron,neutrous/electron,Gerhut/electron,etiktin/electron,kokdemo/electron,fffej/electron,Floato/electron,evgenyzinoviev/electron,kcrt/electron,pirafrank/electron,sky7sea/electron,kazupon/electron,Jonekee/electron,astoilkov/electron,smczk/electron,astoilkov/electron,arusakov/electron,jlhbaseball15/electron,wan-qy/electron,arturts/electron,robinvandernoord/electron,bpasero/electron,voidbridge/electron,thomsonreuters/electron,MaxWhere/electron,bwiggs/electron,seanchas116/electron,pombredanne/electron,miniak/electron,vHanda/electron,tonyganch/electron,nicholasess/electron,bbondy/electron,aaron-goshine/electron,astoilkov/electron,matiasinsaurralde/electron,RobertJGabriel/electron,astoilkov/electron,evgenyzinoviev/electron,bwiggs/electron,greyhwndz/electron,nicholasess/electron,leftstick/electron,RobertJGabriel/electron,leolujuyi/electron,leethomas/electron,dongjoon-hyun/electron,jaanus/electron,jcblw/electron,rreimann/electron,Gerhut/electron,xfstudio/electron,arturts/electron,RIAEvangelist/electron,greyhwndz/electron,gabrielPeart/electron,faizalpribadi/electron,astoilkov/electron,kenmozi/electron,jcblw/electron,brave/electron,arusakov/electron,destan/electron,anko/electron,voidbridge/electron,etiktin/electron,MaxWhere/electron,micalan/electron,brenca/electron,JesselJohn/electron,renaesop/electron,fritx/electron,leftstick/electron,rreimann/electron,takashi/electron,minggo/electron,abhishekgahlot/electron,setzer777/electron,SufianHassan/electron,aaron-goshine/electron,howmuchcomputer/electron,tomashanacek/electron,roadev/electron,bitemyapp/electron,icattlecoder/electron,mjaniszew/electron,kcrt/electron,brenca/electron,greyhwndz/electron,trigrass2/electron,natgolov/electron,thomsonreuters/electron,twolfson/electron,preco21/electron,adcentury/electron,nekuz0r/electron,tylergibson/electron,ianscrivener/electron,tinydew4/electron,biblerule/UMCTelnetHub,lzpfmh/electron,rreimann/electron,brave/muon,mjaniszew/electron,nekuz0r/electron,Floato/electron,shennushi/electron,Jonekee/electron,fritx/electron,JesselJohn/electron,kcrt/electron,sshiting/electron,bobwol/electron,nicobot/electron,nicobot/electron,adcentury/electron,deed02392/electron,rajatsingla28/electron,shiftkey/electron,gerhardberger/electron,posix4e/electron,mrwizard82d1/electron,faizalpribadi/electron,JesselJohn/electron,tonyganch/electron,jhen0409/electron,aaron-goshine/electron,rajatsingla28/electron,fffej/electron,joaomoreno/atom-shell,gerhardberger/electron,minggo/electron,Andrey-Pavlov/electron,tinydew4/electron,mrwizard82d1/electron,abhishekgahlot/electron,nekuz0r/electron,simongregory/electron,RobertJGabriel/electron,roadev/electron,tinydew4/electron,arturts/electron,mirrh/electron,rajatsingla28/electron,mrwizard82d1/electron,the-ress/electron,robinvandernoord/electron,sshiting/electron,fffej/electron,miniak/electron,nekuz0r/electron,iftekeriba/electron,dongjoon-hyun/electron,leethomas/electron,tomashanacek/electron,smczk/electron,brenca/electron,kcrt/electron,ianscrivener/electron,nicobot/electron,arusakov/electron,d-salas/electron,BionicClick/electron,electron/electron,neutrous/electron,thomsonreuters/electron,baiwyc119/electron,jonatasfreitasv/electron,vHanda/electron,leolujuyi/electron,oiledCode/electron,arusakov/electron,xiruibing/electron,jlhbaseball15/electron,smczk/electron,thompsonemerson/electron,seanchas116/electron,pombredanne/electron,posix4e/electron,twolfson/electron,robinvandernoord/electron,aecca/electron,John-Lin/electron,felixrieseberg/electron,chriskdon/electron,bbondy/electron,gabriel/electron,greyhwndz/electron,rajatsingla28/electron,trigrass2/electron,zhakui/electron,tomashanacek/electron,howmuchcomputer/electron,abhishekgahlot/electron,mrwizard82d1/electron,tincan24/electron,carsonmcdonald/electron,baiwyc119/electron,adcentury/electron,Evercoder/electron,shockone/electron,farmisen/electron,thompsonemerson/electron,pirafrank/electron,mirrh/electron,thingsinjars/electron,biblerule/UMCTelnetHub,RIAEvangelist/electron,smczk/electron,aliib/electron,miniak/electron,coderhaoxin/electron,leftstick/electron,jonatasfreitasv/electron,neutrous/electron,tylergibson/electron,pombredanne/electron,MaxWhere/electron,aecca/electron,aliib/electron,aaron-goshine/electron,smczk/electron,anko/electron,Neron-X5/electron,takashi/electron,JussMee15/electron,preco21/electron,dongjoon-hyun/electron,thingsinjars/electron,roadev/electron,BionicClick/electron,simongregory/electron,JussMee15/electron,stevekinney/electron,tonyganch/electron,voidbridge/electron,jtburke/electron,jhen0409/electron,ianscrivener/electron,twolfson/electron,destan/electron,lzpfmh/electron,faizalpribadi/electron,noikiy/electron,kenmozi/electron,iftekeriba/electron,renaesop/electron,bpasero/electron,xfstudio/electron,Floato/electron,howmuchcomputer/electron,saronwei/electron,brave/electron,posix4e/electron,ankitaggarwal011/electron,icattlecoder/electron,jhen0409/electron,rhencke/electron,iftekeriba/electron,IonicaBizauKitchen/electron,miniak/electron,micalan/electron,aichingm/electron,ianscrivener/electron,webmechanicx/electron,tomashanacek/electron,meowlab/electron,kokdemo/electron,miniak/electron,nicholasess/electron,shockone/electron,GoooIce/electron,anko/electron,medixdev/electron,adcentury/electron,vHanda/electron,jonatasfreitasv/electron,shennushi/electron,farmisen/electron,ianscrivener/electron,mirrh/electron,nicobot/electron,zhakui/electron,takashi/electron,minggo/electron,JesselJohn/electron,astoilkov/electron,tonyganch/electron,kenmozi/electron,xiruibing/electron,evgenyzinoviev/electron,JussMee15/electron,eric-seekas/electron,thompsonemerson/electron,leftstick/electron,shiftkey/electron,jjz/electron,pombredanne/electron,pirafrank/electron,tincan24/electron,bpasero/electron,jtburke/electron,deed02392/electron,lzpfmh/electron,gamedevsam/electron,rajatsingla28/electron,gerhardberger/electron,tinydew4/electron,webmechanicx/electron,shockone/electron,Jacobichou/electron,gabriel/electron,farmisen/electron,setzer777/electron,ankitaggarwal011/electron,micalan/electron,electron/electron,Evercoder/electron,seanchas116/electron,renaesop/electron,Andrey-Pavlov/electron,JussMee15/electron,preco21/electron,sshiting/electron,ankitaggarwal011/electron,simongregory/electron,xfstudio/electron,rreimann/electron,kostia/electron,mjaniszew/electron,aichingm/electron,bwiggs/electron,brave/electron,bpasero/electron,RobertJGabriel/electron,MaxWhere/electron,nekuz0r/electron,coderhaoxin/electron,kokdemo/electron,gabriel/electron,jcblw/electron,shiftkey/electron,pirafrank/electron,renaesop/electron,Floato/electron,nicholasess/electron,saronwei/electron,chriskdon/electron,John-Lin/electron,Gerhut/electron,robinvandernoord/electron,the-ress/electron,sshiting/electron,deed02392/electron,mirrh/electron,lzpfmh/electron,SufianHassan/electron,vHanda/electron,rajatsingla28/electron,Neron-X5/electron,gabrielPeart/electron,leolujuyi/electron,stevekinney/electron,kostia/electron,JussMee15/electron,anko/electron,Floato/electron,oiledCode/electron,christian-bromann/electron,robinvandernoord/electron,tylergibson/electron,bitemyapp/electron,Gerhut/electron,thingsinjars/electron,dongjoon-hyun/electron,preco21/electron,eriser/electron,christian-bromann/electron,aaron-goshine/electron,biblerule/UMCTelnetHub,biblerule/UMCTelnetHub,shennushi/electron,BionicClick/electron,biblerule/UMCTelnetHub,noikiy/electron,arturts/electron,gamedevsam/electron,Jonekee/electron,medixdev/electron,mjaniszew/electron,electron/electron,ervinb/electron,tylergibson/electron,brave/muon,BionicClick/electron,coderhaoxin/electron,the-ress/electron,kostia/electron,eric-seekas/electron,shockone/electron,leolujuyi/electron,matiasinsaurralde/electron,kokdemo/electron,bbondy/electron,eriser/electron,sky7sea/electron,saronwei/electron,simongregory/electron,brave/muon,the-ress/electron,shennushi/electron,sky7sea/electron,webmechanicx/electron,GoooIce/electron,eriser/electron,natgolov/electron,tincan24/electron,d-salas/electron,brave/electron,electron/electron,Rokt33r/electron,joaomoreno/atom-shell,anko/electron,carsonmcdonald/electron,JesselJohn/electron,micalan/electron,ianscrivener/electron,carsonmcdonald/electron,jjz/electron,vHanda/electron,arturts/electron,fritx/electron,rreimann/electron,chriskdon/electron,shockone/electron,anko/electron,nekuz0r/electron,pirafrank/electron,carsonmcdonald/electron,Andrey-Pavlov/electron,gabriel/electron,bobwol/electron,mirrh/electron,jlhbaseball15/electron,ervinb/electron,setzer777/electron,digideskio/electron,destan/electron,aecca/electron,aaron-goshine/electron,rhencke/electron,kokdemo/electron,coderhaoxin/electron,gabriel/electron,arusakov/electron,kazupon/electron,leethomas/electron,wan-qy/electron,renaesop/electron,trigrass2/electron,sshiting/electron,digideskio/electron,stevekinney/electron,Rokt33r/electron,voidbridge/electron,shiftkey/electron,voidbridge/electron,fffej/electron,coderhaoxin/electron,icattlecoder/electron,Jacobichou/electron,etiktin/electron,renaesop/electron,baiwyc119/electron,christian-bromann/electron,leftstick/electron,kcrt/electron,setzer777/electron,vHanda/electron,sshiting/electron,gabrielPeart/electron,xiruibing/electron,jjz/electron,medixdev/electron,d-salas/electron,joaomoreno/atom-shell,meowlab/electron,mrwizard82d1/electron,roadev/electron,felixrieseberg/electron,fritx/electron,John-Lin/electron,mjaniszew/electron,matiasinsaurralde/electron,faizalpribadi/electron,setzer777/electron,howmuchcomputer/electron,zhakui/electron,IonicaBizauKitchen/electron,matiasinsaurralde/electron,Rokt33r/electron,rreimann/electron,digideskio/electron,Neron-X5/electron,RIAEvangelist/electron,Andrey-Pavlov/electron,jcblw/electron,arturts/electron,voidbridge/electron,natgolov/electron,thomsonreuters/electron,webmechanicx/electron,jonatasfreitasv/electron,smczk/electron,brave/electron,soulteary/electron,meowlab/electron,deed02392/electron,Jonekee/electron,stevekinney/electron,oiledCode/electron,webmechanicx/electron,brave/muon,the-ress/electron,GoooIce/electron,ervinb/electron,oiledCode/electron,kokdemo/electron,jhen0409/electron,bpasero/electron,wan-qy/electron,tincan24/electron,shennushi/electron,bwiggs/electron,thompsonemerson/electron,bobwol/electron,robinvandernoord/electron,eriser/electron,nicobot/electron,trigrass2/electron,SufianHassan/electron,baiwyc119/electron,GoooIce/electron,jtburke/electron,brenca/electron,Rokt33r/electron,xiruibing/electron,bitemyapp/electron,howmuchcomputer/electron,SufianHassan/electron,bitemyapp/electron,faizalpribadi/electron,leethomas/electron,iftekeriba/electron,preco21/electron,felixrieseberg/electron,brenca/electron,aichingm/electron,baiwyc119/electron,farmisen/electron,oiledCode/electron,GoooIce/electron,tylergibson/electron,electron/electron,destan/electron,fffej/electron,eric-seekas/electron,coderhaoxin/electron,evgenyzinoviev/electron,ankitaggarwal011/electron,soulteary/electron,leethomas/electron,chriskdon/electron,minggo/electron,rhencke/electron,kostia/electron,meowlab/electron,lzpfmh/electron,greyhwndz/electron,etiktin/electron,Gerhut/electron,saronwei/electron,jlhbaseball15/electron,Neron-X5/electron,gerhardberger/electron,Evercoder/electron,d-salas/electron,carsonmcdonald/electron,Andrey-Pavlov/electron,IonicaBizauKitchen/electron,dongjoon-hyun/electron,farmisen/electron,jcblw/electron,takashi/electron,bbondy/electron,digideskio/electron,beni55/electron,xiruibing/electron,nicholasess/electron,rhencke/electron,ervinb/electron,thingsinjars/electron,jaanus/electron,jjz/electron,xfstudio/electron,natgolov/electron,John-Lin/electron,thompsonemerson/electron,matiasinsaurralde/electron,tincan24/electron,roadev/electron,wan-qy/electron,soulteary/electron,JesselJohn/electron,felixrieseberg/electron,shiftkey/electron,posix4e/electron,jjz/electron,icattlecoder/electron,Jacobichou/electron,aliib/electron,baiwyc119/electron,bobwol/electron,jjz/electron,John-Lin/electron,Evercoder/electron,twolfson/electron,joaomoreno/atom-shell,evgenyzinoviev/electron,tonyganch/electron,electron/electron,IonicaBizauKitchen/electron,kostia/electron,joaomoreno/atom-shell,xiruibing/electron,christian-bromann/electron,meowlab/electron,eriser/electron,gabrielPeart/electron,soulteary/electron,simongregory/electron,icattlecoder/electron,fritx/electron,seanchas116/electron,noikiy/electron,Jacobichou/electron,pirafrank/electron,twolfson/electron,Andrey-Pavlov/electron,soulteary/electron,rhencke/electron,gamedevsam/electron,shockone/electron,John-Lin/electron,brave/muon,abhishekgahlot/electron,medixdev/electron,evgenyzinoviev/electron,jtburke/electron,greyhwndz/electron,felixrieseberg/electron,Jonekee/electron,adcentury/electron,webmechanicx/electron,ervinb/electron,christian-bromann/electron,christian-bromann/electron,eric-seekas/electron,posix4e/electron,d-salas/electron,BionicClick/electron,simongregory/electron,abhishekgahlot/electron,Jacobichou/electron,kenmozi/electron,fffej/electron,neutrous/electron,setzer777/electron,neutrous/electron,rhencke/electron,aichingm/electron,GoooIce/electron,zhakui/electron,sky7sea/electron,pombredanne/electron,tylergibson/electron,IonicaBizauKitchen/electron,digideskio/electron,chriskdon/electron,nicholasess/electron,oiledCode/electron,wan-qy/electron,eric-seekas/electron,aecca/electron,kazupon/electron,etiktin/electron,gerhardberger/electron,thingsinjars/electron,xfstudio/electron,SufianHassan/electron,seanchas116/electron,icattlecoder/electron,natgolov/electron,roadev/electron,d-salas/electron,bbondy/electron,jlhbaseball15/electron,brave/electron,adcentury/electron,nicobot/electron,felixrieseberg/electron,kazupon/electron,jhen0409/electron,joaomoreno/atom-shell,leolujuyi/electron,gabrielPeart/electron,eric-seekas/electron,thomsonreuters/electron,Rokt33r/electron,IonicaBizauKitchen/electron,jaanus/electron,trigrass2/electron,soulteary/electron,bitemyapp/electron,minggo/electron,gamedevsam/electron,posix4e/electron,zhakui/electron,brave/muon,bitemyapp/electron,aecca/electron,beni55/electron,Rokt33r/electron,takashi/electron,eriser/electron,chriskdon/electron,JussMee15/electron,aichingm/electron,gamedevsam/electron,tinydew4/electron,Jonekee/electron,RIAEvangelist/electron,ervinb/electron,tomashanacek/electron,micalan/electron,ankitaggarwal011/electron,bobwol/electron,minggo/electron,gerhardberger/electron,BionicClick/electron,noikiy/electron,brenca/electron,noikiy/electron,stevekinney/electron,the-ress/electron,gabrielPeart/electron,saronwei/electron,kenmozi/electron,abhishekgahlot/electron,thomsonreuters/electron,leftstick/electron,tonyganch/electron,RobertJGabriel/electron,zhakui/electron,noikiy/electron,RobertJGabriel/electron,thingsinjars/electron,deed02392/electron,stevekinney/electron,arusakov/electron,Floato/electron,MaxWhere/electron,bwiggs/electron,saronwei/electron,gamedevsam/electron,bwiggs/electron,shennushi/electron,aecca/electron,beni55/electron,Neron-X5/electron,sky7sea/electron,Jacobichou/electron,tomashanacek/electron,gabriel/electron,bpasero/electron,jaanus/electron,dongjoon-hyun/electron,miniak/electron,ankitaggarwal011/electron,biblerule/UMCTelnetHub,meowlab/electron,medixdev/electron,gerhardberger/electron,Gerhut/electron,takashi/electron,jhen0409/electron,fritx/electron,beni55/electron,MaxWhere/electron,wan-qy/electron,jcblw/electron,mjaniszew/electron,carsonmcdonald/electron,RIAEvangelist/electron,digideskio/electron,farmisen/electron,iftekeriba/electron,bbondy/electron,shiftkey/electron,twolfson/electron,neutrous/electron,faizalpribadi/electron,aliib/electron,natgolov/electron,howmuchcomputer/electron,Evercoder/electron,xfstudio/electron,kostia/electron,tincan24/electron,preco21/electron,jtburke/electron,medixdev/electron,kcrt/electron,the-ress/electron,deed02392/electron,aliib/electron,thompsonemerson/electron,Neron-X5/electron,aichingm/electron,mirrh/electron,RIAEvangelist/electron,trigrass2/electron,destan/electron,bpasero/electron,jaanus/electron,etiktin/electron,aliib/electron,seanchas116/electron,kazupon/electron,destan/electron,jlhbaseball15/electron,lzpfmh/electron,sky7sea/electron,jonatasfreitasv/electron,iftekeriba/electron,leethomas/electron