Missing py.typed marker file

[timoffex]

https://typing.readthedocs.io/en/latest/spec/distributing.html#packaging-type-information

Package maintainers who wish to support type checking of their code MUST add a marker file named py.typed to their package supporting typing.

Without this file, mypy emits errors like this on h2 import statements:

Skipping analyzing "h2.config": module is installed, but missing library stubs or py.typed marker Mypy (import-untyped)

[timoffex]

On second thought, maybe this is intentional? I see that not all public APIs are fully typed---for example, mypy infers the type of stream_id and headers on RequestReceived as None because they're not annotated and are set to None in the constructor.

[timoffex]

I am happy to find out that this is being addressed by #1289.