Support for nuproj extension

What was the issue:

Our go-xamarin shared xamarin builder packages, does not know the nuproj project type. This cased issue, like this: failed to create xamarin builder, error: no project found with ID: XYZ

Related github issue:

What we changed to make it better:

As a solution, i updated the go-xamarin package to care only about archivable project types and omit other project types.

Related github pr: