Adding docs

[cnpryer]

I know this is still experimental, but IMO an experiment is only as good as the data it can garner. IME I've noticed a lot of people use a user guide of some form. A lot of the README's contents could be refined into a user guide.

I really like what ruff and hatch have for documentation https://github.com/mitsuhiko/rye/compare/main...cnpryer:rye:docs.

[cnpryer]

To get the ball rolling on this one I’m thinking:

1. Where/how install
2. Overview of features
3. Get Python with Rye
4. Start a project with Rye
5. Adding and removing deps
6. Sync Rye’s current environment
7. Installing a global tool
8. Managing Rye Link to submit issue

Could be ~5min getting started

[cnpryer]

https://cnpryer.github.io/rye/user_guide/

I can submit this as a PR. I just used https://www.mkdocs.org/user-guide/deploying-your-docs/.