Improve PyPI landing page

[dwhswenson]

For some folks, the PyPI project page will be a starting point (Google often prefers PyPI), so ours should be useful. A couple issues:

• Need links to project pages (in particular, this GitHub repo) as part of project metadata. This is a pyproject.toml config.
• README link to docs/aws.md probably needs a full URL. When you click in PyPI, it tries to direct you to https://pypi.org/project/gha-runner/docs/aws.md (which obviously doesn't work).