Allow permanent dismissal of build/debug assets message

[Tyriar]

I have no desire to add the .vscode directory for this project, yet every time I open the folder the extension bugs me. I'd like a way to dismiss it permanently for this PC.

The project in question is a library (no entry point) with a set of tests: https://github.com/gwtw/csharp-data-structures
The message: https://github.com/OmniSharp/omnisharp-vscode/blob/6ecb840f6c9e0d90cf7f10625d0347e6ade6b0b2/src/assets.ts#L126

[DustinCampbell]

There is a new beta of the C# extension available here that includes this feature if you'd like to try it.