Implement PEP 612

[erictraut]

https://www.python.org/dev/peps/pep-0612/

[erictraut]

This is now addressed in Pyright 1.1.37, which I just published.

[hoefling]

@erictraut this is actually pretty awesome that pyright supports PEP 612 already. Right now, it is the only type checker for Python (from the "gang of four" at least) that does correctly resolve paramspecs on decorator factories in my use case. Thank you for the great job you are doing!