Switch to uv for development

[stevepiercy]

I did not update the installation documentation as mentioned as a closing criteria in #906. That's because I found a way to install tox with a plugin uv-tox, which means I can run the tests across multiple Pythons even if I don't already have them installed on my system. And it's fast. It has only two prerequisites, uv and Make.

See https://github.com/sphinx-contrib/httpdomain/blob/main/CONTRIBUTING.md#install-httpdomain-for-development.

That's it. One command make dev and you're set up.

I'm also using uv to build and release a dist, and to run CI with a significant speed boost. I was skeptical about it, but it met my needs and was easy. See the full journey at sphinx-contrib/httpdomain#91.

Anyway, I'd propose to overhaul dev set up to be similar to this. @niccokunzmann what do you think?

Originally posted by @stevepiercy in #906

---

Closing criteria include the following items.

• Edit pyproject.toml, GitHub workflows, tox configuration, and any other files for installation and development.
• Fully document the processes in https://icalendar.readthedocs.io/en/latest/contribute/development.html.

Any other items?

[niccokunzmann]

This can go ahead! Would you like me to do anything? I can review ...

For me, it is important to be able to run different Python versions using tox on my machine so that I can remove errors before they hit the CI.