Update CONTRIBUTING.md
Update CONTRIBUTING.md

Add comment about labels, hint at Development Procedures.
MohmadAyman/RIOT,attdona/RIOT,zhuoshuguo/RIOT,koenning/RIOT,binarylemon/RIOT,Ell-i/RIOT,RBartz/RIOT,kaleb-himes/RIOT,khhhh/RIOT,ThanhVic/RIOT,Josar/RIOT,bartfaizoltan/RIOT,A-Paul/RIOT,thomaseichinger/RIOT,wentaoshang/RIOT,dkm/RIOT,Lotterleben/RIOT,marcosalm/RIOT,basilfx/RIOT,Yonezawa-T2/RIOT,kaspar030/RIOT,emmanuelsearch/RIOT,changbiao/RIOT,rajma996/RIOT,automote/RIOT,A-Paul/RIOT,dhruvvyas90/RIOT,attdona/RIOT,zhuoshuguo/RIOT,dkm/RIOT,herrfz/RIOT-old,MarkXYang/RIOT,wentaoshang/RIOT,MohmadAyman/RIOT,AnonMall/RIOT,stevenj/RIOT,MarkXYang/RIOT,emmanuelsearch/RIOT,robixnai/RIOT,rakendrathapa/RIOT,bartfaizoltan/RIOT,latsku/RIOT,x3ro/RIOT,smlng/RIOT,sumanpanchal/RIOT,jhollister/RIOT,dhruvvyas90/RIOT,beurdouche/RIOT,openkosmosorg/RIOT,syin2/RIOT,latsku/RIOT,emmanuelsearch/RIOT,EmuxEvans/RIOT,herrfz/RIOT,jfischer-phytec-iot/RIOT,ros2/ros2_embedded_riot,avmelnikoff/RIOT,adrianghc/RIOT,tdautc19841202/RIOT,FrancescoErmini/RIOT,syin2/RIOT,tdautc19841202/RIOT,attdona/RIOT,rajma996/RIOT,stevenj/RIOT,BytesGalore/PetersRIOT,MohmadAyman/RIOT,wentaoshang/RIOT,malosek/RIOT,A-Paul/RIOT,attdona/RIOT,haoyangyu/RIOT,dhruvvyas90/RIOT,nsol-nmsu/RIOT,BytesGalore/PetersRIOT,herrfz/RIOT,kushalsingh007/RIOT,syin2/RIOT,FrancescoErmini/RIOT,openkosmosorg/RIOT,jhollister/RIOT,jfischer-phytec-iot/RIOT,yogo1212/RIOT,Lotterleben/RIOT,alex1818/RIOT,Lexandro92/RIOT-CoAP,kYc0o/RIOT,alex1818/RIOT,yogo1212/RIOT,patkan/RIOT,ant9000/RIOT,backenklee/RIOT,kaspar030/RIOT,abkam07/RIOT,BytesGalore/PetersRIOT,yogo1212/RIOT,thomaseichinger/RIOT,dailab/RIOT,kushalsingh007/RIOT,mtausig/RIOT,rousselk/RIOT,arvindpdmn/RIOT,DipSwitch/RIOT,khhhh/RIOT,abkam07/RIOT,thiagohd/RIOT,jferreir/RIOT,kerneltask/RIOT,alex1818/RIOT,BytesGalore/PetersRIOT,l3nko/RIOT,fnack/RIOT,DipSwitch/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,gbarnett/RIOT,ant9000/RIOT,JensErdmann/RIOT,haoyangyu/RIOT,Lotterleben/RIOT,alignan/RIOT,jbeyerstedt/RIOT-OTA-update,changbiao/RIOT,ThanhVic/RIOT,zhuoshuguo/RIOT,toonst/RIOT,biboc/RIOT,malosek/RIOT,ntrtrung/RIOT,brettswann/RIOT,kb2ma/RIOT,msolters/RIOT,fnack/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,LudwigKnuepfer/RIOT,alex1818/RIOT,ant9000/RIOT,avmelnikoff/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,binarylemon/RIOT,jasonatran/RIOT,mfrey/RIOT,sumanpanchal/RIOT,OTAkeys/RIOT,msolters/RIOT,locicontrols/RIOT,Hyungsin/RIOT-OS,robixnai/RIOT,Osblouf/RIOT,MarkXYang/RIOT,koenning/RIOT,ximus/RIOT,openkosmosorg/RIOT,basilfx/RIOT,benoit-canet/RIOT,Darredevil/RIOT,kYc0o/RIOT,Lexandro92/RIOT-CoAP,phiros/RIOT,A-Paul/RIOT,sumanpanchal/RIOT,Lexandro92/RIOT-CoAP,Hyungsin/RIOT-OS,gautric/RIOT,hamilton-mote/RIOT-OS,luciotorre/RIOT,AnonMall/RIOT,josephnoir/RIOT,binarylemon/RIOT,patkan/RIOT,herrfz/RIOT-old,altairpearl/RIOT,shady33/RIOT,katezilla/RIOT,daniel-k/RIOT,hamilton-mote/RIOT-OS,BytesGalore/RIOT,brettswann/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,Lotterleben/RIOT,toonst/RIOT,rfswarm/RIOT,d00616/RIOT,altairpearl/RIOT,OTAkeys/RIOT,emmanuelsearch/RIOT,kushalsingh007/RIOT,abp719/RIOT,syin2/RIOT,rajma996/RIOT,smlng/RIOT,jbeyerstedt/RIOT-OTA-update,automote/RIOT,LudwigOrtmann/RIOT,TobiasFredersdorf/RIOT,plushvoxel/RIOT,MonsterCode8000/RIOT,backenklee/RIOT,Osblouf/RIOT,rfswarm2/RIOT,josephnoir/RIOT,BytesGalore/RIOT,kerneltask/RIOT,ros2/ros2_embedded_riot,luciotorre/RIOT,authmillenon/RIOT,fnack/RIOT,gebart/RIOT,marcosalm/RIOT,PSHIVANI/Riot-Code,avmelnikoff/RIOT,khhhh/RIOT,jhollister/RIOT,adrianghc/RIOT,ks156/RIOT,abkam07/RIOT,kushalsingh007/RIOT,miri64/RIOT,Josar/RIOT,lazytech-org/RIOT,katezilla/RIOT,kerneltask/RIOT,rousselk/RIOT,kb2ma/RIOT,binarylemon/RIOT,hamilton-mote/RIOT-OS,phiros/RIOT,d00616/RIOT,marcosalm/RIOT,herrfz/RIOT-old,centurysys/RIOT,robixnai/RIOT,sgso/RIOT,khhhh/RIOT,neiljay/RIOT,ThanhVic/RIOT,herrfz/RIOT,dkm/RIOT,EmuxEvans/RIOT,fnack/RIOT,x3ro/RIOT,abkam07/RIOT,kerneltask/RIOT,bartfaizoltan/RIOT,haoyangyu/RIOT,mfrey/RIOT,kushalsingh007/RIOT,OlegHahm/RIOT,ks156/RIOT,mtausig/RIOT,asanka-code/RIOT,ros2/ros2_embedded_riot,PSHIVANI/Riot-Code,immesys/RiSyn,Lexandro92/RIOT-CoAP,plushvoxel/RIOT,ThanhVic/RIOT,Yonezawa-T2/RIOT,dailab/RIOT,ks156/RIOT,OlegHahm/RIOT,kYc0o/RIOT,sgso/RIOT,kbumsik/RIOT,AnonMall/RIOT,authmillenon/RIOT,lebrush/RIOT,sgso/RIOT,adjih/RIOT,fnack/RIOT,RBartz/RIOT,josephnoir/RIOT,ThanhVic/RIOT,centurysys/RIOT,toonst/RIOT,cladmi/RIOT,DipSwitch/RIOT,PSHIVANI/Riot-Code,DipSwitch/RIOT,RBartz/RIOT,PSHIVANI/Riot-Code,kaleb-himes/RIOT,plushvoxel/RIOT,gebart/RIOT,alignan/RIOT,Lotterleben/RIOT,centurysys/RIOT,DipSwitch/RIOT,ros2/ros2_embedded_riot,watr-li/RIOT,alex1818/RIOT,rfswarm2/RIOT,jfischer-phytec-iot/RIOT,EmuxEvans/RIOT,kYc0o/RIOT,asanka-code/RIOT,watr-li/RIOT,gbarnett/RIOT,centurysys/RIOT,RIOT-OS/RIOT,biboc/RIOT,altairpearl/RIOT,watr-li/RIOT,l3nko/RIOT,dhruvvyas90/RIOT,sgso/RIOT,lebrush/RIOT,ros2/ros2_embedded_riot,roberthartung/RIOT,herrfz/RIOT-old,attdona/RIOT,jferreir/RIOT,josephnoir/RIOT,LudwigKnuepfer/RIOT,LudwigOrtmann/RIOT,TobiasFredersdorf/RIOT,ros2/ros2_embedded_riot,d00616/RIOT,khhhh/RIOT,wentaoshang/RIOT,phiros/RIOT,herrfz/RIOT-old,hamilton-mote/RIOT-OS,adrianghc/RIOT,1blankz7/RIOT,shady33/RIOT,luciotorre/RIOT,locicontrols/RIOT,neiljay/RIOT,arvindpdmn/RIOT,1blankz7/RIOT,abkam07/RIOT,tfar/RIOT,basilfx/RIOT,RubikonAlpha/RIOT,luciotorre/RIOT,yogo1212/RIOT,Ell-i/RIOT,brettswann/RIOT,tdautc19841202/RIOT,ntrtrung/RIOT,jbeyerstedt/RIOT-OTA-update,Osblouf/RIOT,PSHIVANI/Riot-Code,EmuxEvans/RIOT,adjih/RIOT,aeneby/RIOT,automote/RIOT,mziegert/RIOT,automote/RIOT,gbarnett/RIOT,koenning/RIOT,OlegHahm/RIOT,locicontrols/RIOT,sumanpanchal/RIOT,Josar/RIOT,tfar/RIOT,openkosmosorg/RIOT,mfrey/RIOT,mtausig/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,RIOT-OS/RIOT,rfswarm/RIOT,arvindpdmn/RIOT,gautric/RIOT,rfswarm/RIOT,jasonatran/RIOT,authmillenon/RIOT,MonsterCode8000/RIOT,lebrush/RIOT,aeneby/RIOT,RBartz/RIOT,jferreir/RIOT,alex1818/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,stevenj/RIOT,LudwigOrtmann/RIOT,beurdouche/RIOT,EmuxEvans/RIOT,thiagohd/RIOT,patkan/RIOT,binarylemon/RIOT,jbeyerstedt/RIOT-OTA-update,ant9000/RIOT,benoit-canet/RIOT,jferreir/RIOT,patkan/RIOT,wentaoshang/RIOT,tfar/RIOT,sgso/RIOT,BytesGalore/RIOT,dailab/RIOT,JensErdmann/RIOT,FrancescoErmini/RIOT,AnonMall/RIOT,MarkXYang/RIOT,aeneby/RIOT,shady33/RIOT,abp719/RIOT,neumodisch/RIOT,avmelnikoff/RIOT,thiagohd/RIOT,jremmert-phytec-iot/RIOT,khhhh/RIOT,wentaoshang/RIOT,chris-wood/RIOT,smlng/RIOT,sumanpanchal/RIOT,abp719/RIOT,1blankz7/RIOT,abp719/RIOT,Hyungsin/RIOT-OS,biboc/RIOT,rfswarm/RIOT,MohmadAyman/RIOT,neumodisch/RIOT,watr-li/RIOT,tdautc19841202/RIOT,TobiasFredersdorf/RIOT,RubikonAlpha/RIOT,Yonezawa-T2/RIOT,rfswarm/RIOT,ntrtrung/RIOT,RubikonAlpha/RIOT,jremmert-phytec-iot/RIOT,brettswann/RIOT,immesys/RiSyn,aeneby/RIOT,kbumsik/RIOT,MonsterCode8000/RIOT,kb2ma/RIOT,thomaseichinger/RIOT,rfuentess/RIOT,immesys/RiSyn,rakendrathapa/RIOT,DipSwitch/RIOT,d00616/RIOT,tfar/RIOT,nsol-nmsu/RIOT,kb2ma/RIOT,cladmi/RIOT,RIOT-OS/RIOT,stevenj/RIOT,ximus/RIOT,A-Paul/RIOT,jfischer-phytec-iot/RIOT,jremmert-phytec-iot/RIOT,tdautc19841202/RIOT,phiros/RIOT,ntrtrung/RIOT,gbarnett/RIOT,rakendrathapa/RIOT,ximus/RIOT,roberthartung/RIOT,rfswarm/RIOT,alignan/RIOT,marcosalm/RIOT,robixnai/RIOT,daniel-k/RIOT,authmillenon/RIOT,RubikonAlpha/RIOT,latsku/RIOT,biboc/RIOT,locicontrols/RIOT,neiljay/RIOT,shady33/RIOT,Hyungsin/RIOT-OS,benoit-canet/RIOT,abkam07/RIOT,biboc/RIOT,ximus/RIOT,daniel-k/RIOT,1blankz7/RIOT,rajma996/RIOT,backenklee/RIOT,lebrush/RIOT,ximus/RIOT,thiagohd/RIOT,LudwigKnuepfer/RIOT,mziegert/RIOT,jremmert-phytec-iot/RIOT,ntrtrung/RIOT,kerneltask/RIOT,Yonezawa-T2/RIOT,dailab/RIOT,rfswarm2/RIOT,x3ro/RIOT,lebrush/RIOT,jhollister/RIOT,JensErdmann/RIOT,basilfx/RIOT,gebart/RIOT,kaleb-himes/RIOT,msolters/RIOT,ntrtrung/RIOT,kbumsik/RIOT,openkosmosorg/RIOT,patkan/RIOT,rfuentess/RIOT,koenning/RIOT,luciotorre/RIOT,MonsterCode8000/RIOT,l3nko/RIOT,chris-wood/RIOT,immesys/RiSyn,mziegert/RIOT,rfuentess/RIOT,mziegert/RIOT,plushvoxel/RIOT,OTAkeys/RIOT,l3nko/RIOT,sumanpanchal/RIOT,MohmadAyman/RIOT,rakendrathapa/RIOT,jhollister/RIOT,hamilton-mote/RIOT-OS,gebart/RIOT,lazytech-org/RIOT,bartfaizoltan/RIOT,rfswarm2/RIOT,arvindpdmn/RIOT,OlegHahm/RIOT,immesys/RiSyn,roberthartung/RIOT,neumodisch/RIOT,abp719/RIOT,toonst/RIOT,watr-li/RIOT,automote/RIOT,mziegert/RIOT,AnonMall/RIOT,marcosalm/RIOT,beurdouche/RIOT,koenning/RIOT,msolters/RIOT,Lexandro92/RIOT-CoAP,beurdouche/RIOT,dailab/RIOT,ThanhVic/RIOT,watr-li/RIOT,openkosmosorg/RIOT,TobiasFredersdorf/RIOT,RBartz/RIOT,basilfx/RIOT,d00616/RIOT,gbarnett/RIOT,katezilla/RIOT,latsku/RIOT,nsol-nmsu/RIOT,MonsterCode8000/RIOT,rousselk/RIOT,neumodisch/RIOT,rfuentess/RIOT,daniel-k/RIOT,attdona/RIOT,malosek/RIOT,ximus/RIOT,authmillenon/RIOT,OTAkeys/RIOT,dkm/RIOT,herrfz/RIOT,malosek/RIOT,kushalsingh007/RIOT,LudwigKnuepfer/RIOT,msolters/RIOT,rfswarm2/RIOT,thiagohd/RIOT,robixnai/RIOT,zhuoshuguo/RIOT,avmelnikoff/RIOT,Osblouf/RIOT,alignan/RIOT,l3nko/RIOT,authmillenon/RIOT,adrianghc/RIOT,miri64/RIOT,ks156/RIOT,smlng/RIOT,asanka-code/RIOT,jasonatran/RIOT,phiros/RIOT,altairpearl/RIOT,locicontrols/RIOT,kaleb-himes/RIOT,chris-wood/RIOT,malosek/RIOT,stevenj/RIOT,immesys/RiSyn,RIOT-OS/RIOT,benoit-canet/RIOT,cladmi/RIOT,rousselk/RIOT,binarylemon/RIOT,miri64/RIOT,asanka-code/RIOT,emmanuelsearch/RIOT,lazytech-org/RIOT,dhruvvyas90/RIOT,jferreir/RIOT,daniel-k/RIOT,OTAkeys/RIOT,jasonatran/RIOT,locicontrols/RIOT,changbiao/RIOT,mfrey/RIOT,shady33/RIOT,kaleb-himes/RIOT,rakendrathapa/RIOT,Ell-i/RIOT,JensErdmann/RIOT,FrancescoErmini/RIOT,katezilla/RIOT,sgso/RIOT,BytesGalore/PetersRIOT,syin2/RIOT,MonsterCode8000/RIOT,herrfz/RIOT,adjih/RIOT,backenklee/RIOT,jasonatran/RIOT,zhuoshuguo/RIOT,rousselk/RIOT,x3ro/RIOT,lazytech-org/RIOT,arvindpdmn/RIOT,latsku/RIOT,roberthartung/RIOT,kaspar030/RIOT,mtausig/RIOT,bartfaizoltan/RIOT,neumodisch/RIOT,thomaseichinger/RIOT,kYc0o/RIOT,rfuentess/RIOT,gbarnett/RIOT,koenning/RIOT,lazytech-org/RIOT,kbumsik/RIOT,robixnai/RIOT,brettswann/RIOT,Ell-i/RIOT,LudwigOrtmann/RIOT,altairpearl/RIOT,LudwigOrtmann/RIOT,FrancescoErmini/RIOT,roberthartung/RIOT,abp719/RIOT,altairpearl/RIOT,phiros/RIOT,dhruvvyas90/RIOT,BytesGalore/RIOT,herrfz/RIOT,yogo1212/RIOT,adjih/RIOT,beurdouche/RIOT,tdautc19841202/RIOT,MarkXYang/RIOT,Osblouf/RIOT,aeneby/RIOT,marcosalm/RIOT,l3nko/RIOT,Josar/RIOT,centurysys/RIOT,shady33/RIOT,nsol-nmsu/RIOT,smlng/RIOT,thiagohd/RIOT,RBartz/RIOT,backenklee/RIOT,JensErdmann/RIOT,MohmadAyman/RIOT,ros2/ros2_embedded_riot,brettswann/RIOT,gautric/RIOT,mfrey/RIOT,miri64/RIOT,dkm/RIOT,centurysys/RIOT,BytesGalore/PetersRIOT,tfar/RIOT,mtausig/RIOT,kaspar030/RIOT,LudwigKnuepfer/RIOT,emmanuelsearch/RIOT,RubikonAlpha/RIOT,jferreir/RIOT,toonst/RIOT,changbiao/RIOT,rfswarm2/RIOT,rajma996/RIOT,Darredevil/RIOT,Yonezawa-T2/RIOT,haoyangyu/RIOT,fnack/RIOT,cladmi/RIOT,Darredevil/RIOT,changbiao/RIOT,bartfaizoltan/RIOT,adrianghc/RIOT,adjih/RIOT,patkan/RIOT,jhollister/RIOT,chris-wood/RIOT,d00616/RIOT,rajma996/RIOT,lebrush/RIOT,asanka-code/RIOT,Osblouf/RIOT,MarkXYang/RIOT,Hyungsin/RIOT-OS,TobiasFredersdorf/RIOT,neiljay/RIOT,changbiao/RIOT,BytesGalore/PetersRIOT,1blankz7/RIOT,Darredevil/RIOT,miri64/RIOT,msolters/RIOT,JensErdmann/RIOT,gautric/RIOT,Lotterleben/RIOT,benoit-canet/RIOT,luciotorre/RIOT,Lotterleben/RIOT,haoyangyu/RIOT,gautric/RIOT,AnonMall/RIOT,benoit-canet/RIOT,RubikonAlpha/RIOT,malosek/RIOT,jfischer-phytec-iot/RIOT,Darredevil/RIOT,daniel-k/RIOT,jremmert-phytec-iot/RIOT,BytesGalore/RIOT,asanka-code/RIOT,jremmert-phytec-iot/RIOT,Yonezawa-T2/RIOT,neiljay/RIOT,kbumsik/RIOT,katezilla/RIOT,latsku/RIOT,LudwigOrtmann/RIOT,cladmi/RIOT,locicontrols/RIOT,yogo1212/RIOT,plushvoxel/RIOT,x3ro/RIOT,rousselk/RIOT,jbeyerstedt/RIOT-OTA-update,PSHIVANI/Riot-Code,haoyangyu/RIOT,chris-wood/RIOT,Josar/RIOT,OlegHahm/RIOT,rakendrathapa/RIOT,zhuoshuguo/RIOT,Darredevil/RIOT,Lexandro92/RIOT-CoAP,nsol-nmsu/RIOT,FrancescoErmini/RIOT,kaspar030/RIOT,kb2ma/RIOT,ks156/RIOT,neumodisch/RIOT,1blankz7/RIOT,alignan/RIOT,ant9000/RIOT,thomaseichinger/RIOT,Ell-i/RIOT,automote/RIOT,gebart/RIOT,arvindpdmn/RIOT,EmuxEvans/RIOT,chris-wood/RIOT,stevenj/RIOT,mziegert/RIOT