See #2, #1385 for context. Superseeds #1565.
This is the minimal core Sphinx support part, adding a bare minimum of useful things to get Sphinx to build and deploy, whilst not affecting the current build system. There is no theming or custom parsing needed to properly deal with PEPs.
- `build.py` - build script
- `conf.py` - Sphinx configuration
- `Makefile` - new targets for Sphinx
- `.gitignore` - add ignores for `venv` and `package` directories
- `contents.rst` - Sphinx page to discover all PEPs
- `deploy-gh-pages.yaml` - builds and deploys to github pages
- `requirements.txt`