Related to #88

Note: It seems like there was a lot of white spaces in the original files and because my IDEs remove them it make a lot of noise in the diff.

It is possible in GitHub to hide the white space to make it easier to read the diff:

If that's really a problem, I could redo all the changes from master but I would prefer to just remove the white spaces from the files and add a .editorconfig file to ensure the behaviour across the different IDEs/developer machine. .editorconfig is file understand by most of the IDEs/Editors allowing to configure things like tabs size, removal of white space, etc.

Current status:

• Upgrade to FCS 39
• Change the project to target net5.0
• [ ] Change the path in the extension to use net5.0 instead of netcoreapp3.0 release
• Fix warnings
  • Warnings due to Array decomposition

- "Possible incorrect indentation"

• There is a regression in tests/FSharpLanguageServer.Tests. The tests testing is .fsx files works is failing but it is not failing on master branch
• There is a failing test in tests/ProjectCracker.Tests but it is already failing in the master branch so not related to my changes. I will see if I can fix it or if I move directly to test Ionide/dotnet-proj library

This test starting failing when net5.0 has been introduced on the CI machine. On this build we can see that the Windows build is green while the Linux build is red.

The difference is Windows build doesn't have net5 while Linux does:

• I have a new warning when compiling the projects

fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj : warning NU1605: Detected package downgrade: FSharp.Core from 5.0.1 to 5.0.0. Reference the package directly from the project to select a different version. 
fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj : warning NU1605:  FSharpLanguageServer -> FSharp.Compiler.Service 39.0.0 -> FSharp.Core (= 5.0.1)
fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj : warning NU1605:  FSharpLanguageServer -> FSharp.Core (>= 5.0.0)

I don't know why I have this problem. I tried forcing FSharp.Core version in the fsproj but still get the warning.

When executing dotnet add package FSharp.Core, I have this error:

$ dotnet add src/FSharpLanguageServer/ package FSharp.Core
  Determining projects to restore...
  Writing C:\Users\Maxime\AppData\Local\Temp\tmpFC1C.tmp
info : Adding PackageReference for package 'FSharp.Core' into project 'C:\Users\Maxime\Documents\Workspace\Github\fsprojects\fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj'.
info :   CACHE https://api.nuget.org/v3/registration5-gz-semver2/fsharp.core/index.json
info : Restoring packages for C:\Users\Maxime\Documents\Workspace\Github\fsprojects\fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj...
info : Package 'FSharp.Core' is compatible with all the specified frameworks in project 'C:\Users\Maxime\Documents\Workspace\Github\fsprojects\fsharp-language-server\src\FSharpLanguageServer\FSharpLanguageServer.fsproj'.
error: Error while performing Update for package 'FSharp.Core'. Cannot edit items in imported files - 
error:   Item 'PackageReference' for 'FSharp.Core' in Imported file 'C:\Program Files\dotnet\sdk\5.0.202\FSharp\Microsoft.FSharp.NetSdk.props'.