[Feature Request] Add `py.typed` and type annotations to Python package

Describe the feature request

It would be great if the project included type annotations and a py.typed file. Currently, running Mypy generates an error:

main.py:7: error: Skipping analyzing "onnxruntime": module is installed, but missing library stubs or py.typed marker  [import-untyped]
main.py:7: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

• https://mypy.readthedocs.io/en/stable/installed_packages.html
• https://peps.python.org/pep-0561/

Describe scenario use case

Running Mypy against a Python application that imports onnxruntime to ensure proper use.