Add Clang Stubfiles

[Vizonex]

For the longest time using clang as been rather annoying on python 3 since the entire library lacks typehinting and I have been using clang for developing bindings as well as other CPython & Cython Related projects. I have already attempted to make a pull request to the python clang maintainers to add stub files with no avail or responses. So I thought moving this here would be a better temporary solution for the time being. Feel free to provide me with feedback if there's anything I need to change as I plan to add a few more in the future such as the third party library pyduktape2 which currently has had suffered from the same outcome.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[srittau]

Please note that you will need a stubs/clang/METADATA.toml file describing these stubs. See CONTRIBUTING.md for more information and the other METADATA.toml files in this repository for examples.

[srittau]

Another build failure is due to the pyright strict config. This should be solved by adding stubs/clang to pyrightconfig.stricter.json's exclude key. There are also some mypy errors here:

https://github.com/python/typeshed/actions/runs/15101805593/job/42443806988?pr=13933

[brianschubert]

Marking this as a draft for now since CI isn't passing