[FR] Missing type hints

[JohnGale87]

Is your feature request related to a problem? Please describe.
Mypy is reporting:

Skipping analyzing "firebase_admin": module is installed, but missing library stubs or py.typed marker
Mypy[import-untyped](https://mypy.readthedocs.io/en/latest/_refs.html#code-import-untyped)

See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
Mypy[note](https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports)

Describe the solution you'd like
I would like Mypy to be able to provide valid type hints and stop warning me that it can't.

Describe alternatives you've considered
Use # type: ignore to ignore the warning.

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.