Add py.typed marker

[leonsmith]

When pulling this project into a typed project, mypy refuses to use the types present becuase its missing the py.typed marker.

You end up with the following error:

error: Skipping analyzing "typeid": module is installed, but missing library stubs or py.typed marker  [import-untyped]
note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

Super simple to fix by adding a py.typed file to the project.

You can of course bypass this and force mypy to still use the types with the following config but it would be nice to work out of the box considering it already has types 😄

[[tool.mypy.overrides]]
module = ["typeid.*"]
follow_untyped_imports = true

More reading:
https://mypy.readthedocs.io/en/stable/installed_packages.html#creating-pep-561-compatible-packages
https://blog.whtsky.me/tech/2021/dont-forget-py.typed-for-your-typed-python-package/
https://peps.python.org/pep-0561/