Update src/app/FakeLib/StringHelper.fs
Update src/app/FakeLib/StringHelper.fs

Adding the DecodeBase64Utf8String function to the string helper

JonCanning/FAKE,satsuper/FAKE,rflechner/FAKE,ctaggart/FAKE,MichalDepta/FAKE,beeker/FAKE,hitesh97/FAKE,ctaggart/FAKE,xavierzwirtz/FAKE,dlsteuer/FAKE,yonglehou/FAKE,daniel-chambers/FAKE,pmcvtm/FAKE,jayp33/FAKE,ovu/FAKE,xavierzwirtz/FAKE,NaseUkolyCZ/FAKE,mfalda/FAKE,yonglehou/FAKE,darrelmiller/FAKE,tpetricek/FAKE,modulexcite/FAKE,xavierzwirtz/FAKE,haithemaraissia/FAKE,ilkerde/FAKE,haithemaraissia/FAKE,molinch/FAKE,beeker/FAKE,jayp33/FAKE,molinch/FAKE,naveensrinivasan/FAKE,NaseUkolyCZ/FAKE,ilkerde/FAKE,daniel-chambers/FAKE,mglodack/FAKE,Kazark/FAKE,mfalda/FAKE,beeker/FAKE,mat-mcloughlin/FAKE,warnergodfrey/FAKE,JonCanning/FAKE,daniel-chambers/FAKE,Kazark/FAKE,haithemaraissia/FAKE,featuresnap/FAKE,naveensrinivasan/FAKE,satsuper/FAKE,dmorgan3405/FAKE,RMCKirby/FAKE,yonglehou/FAKE,warnergodfrey/FAKE,wooga/FAKE,MiloszKrajewski/FAKE,rflechner/FAKE,wooga/FAKE,philipcpresley/FAKE,mglodack/FAKE,RMCKirby/FAKE,warnergodfrey/FAKE,wooga/FAKE,darrelmiller/FAKE,yonglehou/FAKE,haithemaraissia/FAKE,philipcpresley/FAKE,dmorgan3405/FAKE,mat-mcloughlin/FAKE,tpetricek/FAKE,gareth-evans/FAKE,neoeinstein/FAKE,leflings/FAKE,pacificIT/FAKE,rflechner/FAKE,satsuper/FAKE,dlsteuer/FAKE,modulexcite/FAKE,RMCKirby/FAKE,pmcvtm/FAKE,ArturDorochowicz/FAKE,darrelmiller/FAKE,beeker/FAKE,mfalda/FAKE,gareth-evans/FAKE,molinch/FAKE,NaseUkolyCZ/FAKE,brianary/FAKE,rflechner/FAKE,naveensrinivasan/FAKE,brianary/FAKE,warnergodfrey/FAKE,leflings/FAKE,daniel-chambers/FAKE,pacificIT/FAKE,MiloszKrajewski/FAKE,pmcvtm/FAKE,JonCanning/FAKE,dmorgan3405/FAKE,NaseUkolyCZ/FAKE,hitesh97/FAKE,ilkerde/FAKE,JonCanning/FAKE,pmcvtm/FAKE,modulexcite/FAKE,hitesh97/FAKE,neoeinstein/FAKE,darrelmiller/FAKE,leflings/FAKE,wooga/FAKE,Kazark/FAKE,ArturDorochowicz/FAKE,featuresnap/FAKE,dlsteuer/FAKE,brianary/FAKE,ArturDorochowicz/FAKE,pacificIT/FAKE,MiloszKrajewski/FAKE,featuresnap/FAKE,ArturDorochowicz/FAKE,jayp33/FAKE,dlsteuer/FAKE,mat-mcloughlin/FAKE,hitesh97/FAKE,tpetricek/FAKE,ctaggart/FAKE,leflings/FAKE,MichalDepta/FAKE,molinch/FAKE,mglodack/FAKE,modulexcite/FAKE,pacificIT/FAKE,ovu/FAKE,RMCKirby/FAKE,mfalda/FAKE,ilkerde/FAKE,philipcpresley/FAKE,gareth-evans/FAKE,MiloszKrajewski/FAKE,neoeinstein/FAKE,MichalDepta/FAKE,tpetricek/FAKE,MichalDepta/FAKE,satsuper/FAKE,philipcpresley/FAKE,jayp33/FAKE,dmorgan3405/FAKE,featuresnap/FAKE,ovu/FAKE,mat-mcloughlin/FAKE,ctaggart/FAKE,brianary/FAKE,gareth-evans/FAKE,ovu/FAKE,naveensrinivasan/FAKE,neoeinstein/FAKE,mglodack/FAKE,xavierzwirtz/FAKE,Kazark/FAKE