Improve repo development experience on VS Code and VS4Mac

[captainsafia]

Our current setup experience for the aspnetcore repo is designed to work best with Visual Studio (thinking about things like our startvs scripts, our solution filters, debugging through multiple projects, etc).

We should invest some time into making the experience on VS Code and VS4Mac good for new contributors. This can include things like:

• Adding more VS Code launch configurations for different project scenarios (e.g. running test apps, tests, etc)
• Providing a more complete set of default extensions for VS Code
• Adding git hooks to alert users of common issues in their PR (e.g. bad formatting, no API updates, etc)

...and probably more.

[Pilchie]

We should also investigate adding a devcontainer.json so that VSCode remote can get a container with all of our dependencies in it more easily.

• https://code.visualstudio.com/docs/remote/devcontainerjson-reference

[wtgodbe]

@captainsafia what are your thoughts on the current state of this?

[captainsafia]

I think we can probably close this out.

With C# Dev Kit, the experience for running tests in the repo is much improved.

The one hiccup is that VS Code doesn't have the best support for slnf files at the moment so you end up having to deal with the .sln files that the extension auto-generates but that's something that might evolve on the extension side.