Fixes this really annoying behavior where the served documentation would
not reflect changes to the mkdocs template file (where we store all of
our actual configuration)
ref https://github.com/mkdocs/mkdocs/pull/2642
## Summary
We want to have consistency between the Ruff and uv documentation for
the upcoming release. We don't love the Ruff docs, but we'd rather have
consistency and then work towards improving them both, rather than have
two very-different documentation sites that both have weaknesses.
The setup here is simpler than in Ruff as: (1) we don't yet generate any
docs from Rust and (2) we don't try to reuse the README in the uv
documentation (which adds a lot of complexity in Ruff). So the change
here is mostly a 1-to-1 port to MkDocs.
## Test Plan
