Add a py.typed file for PEP 561 compliance

[appleby]

This ensures that mypy can "find" the rcpq package when checking type annotations from pyquil (or any other package that uses rpcq).

This is tangentially related to work in rigetti/pyquil#999

https://www.python.org/dev/peps/pep-0561/
https://mypy.readthedocs.io/en/latest/installed_packages.html#making-pep-561-compatible-packages

[notmgsk]

Strange. But you gotta do what you gotta do.

[appleby]

Strange. But you gotta do what you gotta do.

Indeed. mypy also seems to be confused by rpcq's use of ruamel.yaml, claiming it can't find the package even though ruamel includes a py.typed file. Maybe because ruamel is a "namespace" package? 🤷‍♂ Haven't managed to track it down yet. Weirdly, running mypy from the rpcq directory doesn't complain about missing ruamel, but running from pyquil, which only transitively depends on ruamel via rpcq, dumps tons of warnings about it.

[stylewarning]

eye_roll.jpg