Update .gitignore (#4127)
Update .gitignore (#4127)

Fixes this: https://github.com/Microsoft/visualfsharp/pull/4119#discussion_r157330153
brettfo/visualfsharp,syeerzy/visualfsharp,dsyme/fsharp,syeerzy/visualfsharp,dsyme/fsharp,fsharp/fsharp,dsyme/fsharp,brettfo/visualfsharp,cloudRoutine/FSharp.Compiler.Service,brettfo/visualfsharp,cloudRoutine/FSharp.Compiler.Service,fsharp/fsharp,Jand42/FSharp.Compiler.Service,syeerzy/visualfsharp,dsyme/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,dsyme/FSharp.Compiler.Service,brettfo/visualfsharp,syeerzy/visualfsharp,dsyme/fsharp,brettfo/visualfsharp,dsyme/fsharp,fsharp/fsharp,brettfo/visualfsharp,ncave/FSharp.Compiler.Service,syeerzy/visualfsharp,syeerzy/visualfsharp,ncave/FSharp.Compiler.Service,dsyme/FSharp.Compiler.Service,dsyme/fsharp,dsyme/fsharp,Jand42/FSharp.Compiler.Service,ncave/FSharp.Compiler.Service,Jand42/FSharp.Compiler.Service