Include a py.typed file so mypy works for downstream packages

[rumpelsepp]

@felixdivo We might need to include a py.typed file so mypy works for downstream packages. But i'm not sure if it causes problems since can.interfaces is not really well annotated.

Originally posted by @zariiii9003 in #1227 (comment)

[felixdivo]

Hm, good point. I can look into it next week. 🙂

[felixdivo]

Okay, after adding the py.typed file, I do not get the following error any more:

root@260d806091e3:/home# mypy test.py
test.py:1: error: Skipping analyzing "can": module is installed, but missing library stubs or py.typed marker
test.py:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Found 1 error in 1 file (checked 1 source file)

[felixdivo]

I dont't really know about the missing parts, but I'd suppose its not too much of a concern. Most usage of the library will probably revolve around the core classes anyways. I suggest just adding it and waiting for feedback.

It also seems like it should be fine to just distribute partial type info. The partial marker appears to meant for stub packages only.