Build manywheel in GitHub Actions

[sritchie]

Here's some prior art that I think will work for us: https://github.com/OpenNMT/CTranslate2/blob/master/.github/workflows/ci.yml#L156-L199

Notice the setup scripts that manually install CUDA into the docker environment used by https://cibuildwheel.readthedocs.io/en/latest/working-examples/.