Enable static type checking for our published Python libraries

[jtherrmann]

Jira: https://asfdaac.atlassian.net/browse/TOOL-3457

Note: The above link is accessible only to members of ASF.

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Although we have added our mypy workflow to all of our Python repos, including our distributed packages such as the hyp3-sdk (see our Releasing HyP3 SDK and other packages wiki article for a complete list), we haven't yet enabled library type support for our distributed packages, so if someone imports one of our modules in their code (e.g. from hyp3_sdk import HyP3), they'll get a missing library stubs or py.typed marker error and the imported module will default to type Any (dynamic typing).

From Creating PEP 561 compatible packages, I think enabling static type checking for our published libraries is just:

1. Ensure that all public functions and classes within the package module have type annotations.
2. Add a py.typed file to the package directory.

Also see https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-library-stubs-or-py-typed-marker