Allow add-ons to specify pip packages to be added to the add-on on compile

[seanbudd]

Originally from nvdaaddons#70

I think this would be a handy feature for add-on authors.
Having to maintain your pip packages is not the easiest manual process.
It would be nice to have requirements.txt or pyproject.toml file that is used to fetch dependencies and place them in the appropriate location when building an add-on

[hwf1324]

Yes, we should be able to do this with pip, e.g. pip install [--no-deps] --no-compile -t lib -r requirements.txt --platform win_amd64 --python-version 3.13.