Add async version of IVsSingleFileGenerator

[davkean]

XAML designer team want the ability to implement an async single file generator so that they update source files in background, instead of being blocked by them such as when switching source tabs.

Preferably this would work for both legacy and CPS-based projects.

[ymassad]

Are there any workarounds for this?

[rezanid]

I found the IVsSingleFileGeneratorAsync, but there is no sample or any documentation on how to implement. I did an implementation similar to IVsSingleFileGenerator and same kind of registration, but it looks like VS is completely ignoring it. @Davkin, did you receive any feedback / workaround?