doc: fix grammar in doc/files.md
doc: fix grammar in doc/files.md

qtumproject/qtum,jlopp/statoshi,Xekyo/bitcoin,andreaskern/bitcoin,mm-s/bitcoin,kallewoof/bitcoin,andreaskern/bitcoin,prusnak/bitcoin,MarcoFalke/bitcoin,kallewoof/bitcoin,jambolo/bitcoin,domob1812/bitcoin,JeremyRubin/bitcoin,bitcoinsSG/bitcoin,fujicoin/fujicoin,JeremyRubin/bitcoin,jamesob/bitcoin,sipsorcery/bitcoin,sstone/bitcoin,qtumproject/qtum,bitcoin/bitcoin,andreaskern/bitcoin,fujicoin/fujicoin,ElementsProject/elements,mruddy/bitcoin,bitcoin/bitcoin,apoelstra/bitcoin,MarcoFalke/bitcoin,domob1812/namecore,particl/particl-core,pataquets/namecoin-core,namecoin/namecore,pataquets/namecoin-core,pataquets/namecoin-core,prusnak/bitcoin,anditto/bitcoin,domob1812/bitcoin,ElementsProject/elements,domob1812/namecore,dscotese/bitcoin,andreaskern/bitcoin,GroestlCoin/bitcoin,apoelstra/bitcoin,mruddy/bitcoin,namecoin/namecoin-core,GroestlCoin/bitcoin,instagibbs/bitcoin,particl/particl-core,GroestlCoin/bitcoin,apoelstra/bitcoin,AkioNak/bitcoin,tecnovert/particl-core,sstone/bitcoin,fujicoin/fujicoin,prusnak/bitcoin,bitcoinsSG/bitcoin,ajtowns/bitcoin,mm-s/bitcoin,instagibbs/bitcoin,Xekyo/bitcoin,yenliangl/bitcoin,Xekyo/bitcoin,bitcoinsSG/bitcoin,namecoin/namecore,fanquake/bitcoin,pataquets/namecoin-core,qtumproject/qtum,MarcoFalke/bitcoin,pataquets/namecoin-core,domob1812/bitcoin,instagibbs/bitcoin,Xekyo/bitcoin,achow101/bitcoin,lateminer/bitcoin,jlopp/statoshi,ajtowns/bitcoin,namecoin/namecore,jlopp/statoshi,qtumproject/qtum,dscotese/bitcoin,prusnak/bitcoin,lateminer/bitcoin,ajtowns/bitcoin,lateminer/bitcoin,bitcoinknots/bitcoin,instagibbs/bitcoin,andreaskern/bitcoin,bitcoin/bitcoin,ElementsProject/elements,GroestlCoin/bitcoin,dscotese/bitcoin,achow101/bitcoin,jambolo/bitcoin,bitcoin/bitcoin,ajtowns/bitcoin,particl/particl-core,yenliangl/bitcoin,lateminer/bitcoin,particl/particl-core,ElementsProject/elements,sipsorcery/bitcoin,achow101/bitcoin,GroestlCoin/bitcoin,instagibbs/bitcoin,MarcoFalke/bitcoin,jambolo/bitcoin,domob1812/namecore,MarcoFalke/bitcoin,yenliangl/bitcoin,qtumproject/qtum,dscotese/bitcoin,fujicoin/fujicoin,fujicoin/fujicoin,dscotese/bitcoin,prusnak/bitcoin,namecoin/namecoin-core,JeremyRubin/bitcoin,bitcoinsSG/bitcoin,GroestlCoin/bitcoin,qtumproject/qtum,apoelstra/bitcoin,kallewoof/bitcoin,instagibbs/bitcoin,mruddy/bitcoin,ajtowns/bitcoin,jamesob/bitcoin,tecnovert/particl-core,fanquake/bitcoin,jambolo/bitcoin,bitcoinsSG/bitcoin,tecnovert/particl-core,mruddy/bitcoin,sipsorcery/bitcoin,sipsorcery/bitcoin,sstone/bitcoin,domob1812/bitcoin,JeremyRubin/bitcoin,bitcoinknots/bitcoin,bitcoin/bitcoin,qtumproject/qtum,lateminer/bitcoin,anditto/bitcoin,apoelstra/bitcoin,anditto/bitcoin,GroestlCoin/GroestlCoin,MarcoFalke/bitcoin,jamesob/bitcoin,mruddy/bitcoin,kallewoof/bitcoin,particl/particl-core,tecnovert/particl-core,AkioNak/bitcoin,domob1812/bitcoin,ElementsProject/elements,yenliangl/bitcoin,sipsorcery/bitcoin,mm-s/bitcoin,sipsorcery/bitcoin,achow101/bitcoin,andreaskern/bitcoin,jlopp/statoshi,Xekyo/bitcoin,AkioNak/bitcoin,fanquake/bitcoin,tecnovert/particl-core,fanquake/bitcoin,fanquake/bitcoin,dscotese/bitcoin,AkioNak/bitcoin,jlopp/statoshi,mm-s/bitcoin,fanquake/bitcoin,sstone/bitcoin,domob1812/namecore,mruddy/bitcoin,anditto/bitcoin,GroestlCoin/GroestlCoin,GroestlCoin/GroestlCoin,namecoin/namecore,pataquets/namecoin-core,namecoin/namecoin-core,sstone/bitcoin,particl/particl-core,GroestlCoin/GroestlCoin,GroestlCoin/GroestlCoin,fujicoin/fujicoin,ajtowns/bitcoin,mm-s/bitcoin,namecoin/namecoin-core,lateminer/bitcoin,achow101/bitcoin,achow101/bitcoin,tecnovert/particl-core,domob1812/namecore,namecoin/namecoin-core,jamesob/bitcoin,namecoin/namecore,bitcoinsSG/bitcoin,AkioNak/bitcoin,apoelstra/bitcoin,jamesob/bitcoin,mm-s/bitcoin,bitcoinknots/bitcoin,JeremyRubin/bitcoin,GroestlCoin/GroestlCoin,ElementsProject/elements,anditto/bitcoin,bitcoin/bitcoin,jamesob/bitcoin,AkioNak/bitcoin,jambolo/bitcoin,sstone/bitcoin,domob1812/namecore,jlopp/statoshi,jambolo/bitcoin,yenliangl/bitcoin,prusnak/bitcoin,namecoin/namecore,bitcoinknots/bitcoin,kallewoof/bitcoin,domob1812/bitcoin,anditto/bitcoin,kallewoof/bitcoin,bitcoinknots/bitcoin,Xekyo/bitcoin,JeremyRubin/bitcoin,namecoin/namecoin-core,yenliangl/bitcoin