Add global.json for `dnu restore` from root
Add global.json for `dnu restore` from root

jsoref/PowerShell,kmosher/PowerShell,daxian-dbw/PowerShell,JamesWTruher/PowerShell-1,bingbing8/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,bingbing8/PowerShell,JamesWTruher/PowerShell-1,bmanikm/PowerShell,KarolKaczmarek/PowerShell,KarolKaczmarek/PowerShell,daxian-dbw/PowerShell,PaulHigin/PowerShell,PaulHigin/PowerShell,jsoref/PowerShell,TravisEz13/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,TravisEz13/PowerShell,bmanikm/PowerShell,KarolKaczmarek/PowerShell,daxian-dbw/PowerShell,bingbing8/PowerShell,PaulHigin/PowerShell,bmanikm/PowerShell,jsoref/PowerShell,bingbing8/PowerShell,TravisEz13/PowerShell,KarolKaczmarek/PowerShell,TravisEz13/PowerShell,kmosher/PowerShell,JamesWTruher/PowerShell-1,bmanikm/PowerShell,JamesWTruher/PowerShell-1,bingbing8/PowerShell,kmosher/PowerShell,bmanikm/PowerShell,kmosher/PowerShell,kmosher/PowerShell,jsoref/PowerShell