Add a .vsconfig file to the repo root

[natemcmaster]

See https://devblogs.microsoft.com/setup/configure-visual-studio-across-your-organization-with-vsconfig/

Work required:

• convert https://github.com/aspnet/AspNetCore/blob/master/eng/scripts/vs.json into the proper format and ensure InstallVisualStudio.ps1 still works.
• review the list of required workloads and see if we can remove any. Candidates:
  • Microsoft.VisualStudio.Workload.VisualStudioExtension,
  • Microsoft.VisualStudio.Component.Azure.Storage.Emulator
  • all of the old Microsoft.Net.Component.(version).TargetingPack workloads

[rynowak]

That's pretty dope that they added this 👍

[JunTaoLuo]

Unassigning myself since this is backlogged

[dougbu]

@Pilchie fixed this in f34033a