Implement platform-specific extensions

[isidorn]

Hi PM from the VS Code team here 👋

VS Code now supports platform specific extensions. More details can be found here. This should be very useful for C# since currently you download platform binaries after activation.

This document has all the details:
https://code.visualstudio.com/api/working-with-extensions/publishing-extension#platformspecific-extensions

Let me know if I can help.

fyi @gregg-miskelly

[isidorn]

@gregg-miskelly thanks a lot for doing this 👏