Set up versioning for user guide

[kotval]

https://squidfunk.github.io/mkdocs-material/setup/setting-up-versioning/

Once you build an application with polars, you're often stuck on a version untili you need to upgrade. Not being able to see the docs from the version you are using is a pain, and upgrading can break other things. Please set up the version tags in mkdocs material as described in the link above.

[stinodego]

The Python API reference now has versioning support.

It would be nice if the user guide could also have versioning support. There are a few issues though:

• The user guide is built with MkDocs, while the API reference is built with Sphinx. Versioning with Mike is not compatible with the way Sphinx docs are currently versioned.
• The user guide contains docs for both Rust and Python. Should the user guide be versioned together with Python, or with Rust? It's not very clear how this should be done, unless we synchronize our Rust and Python releases.

[bhogan-mitre]

Related: when the API reference gives a choice of "dev", "0.19 (stable)", or "0.18", it's not clear to the user exactly what that refers to. For example, does 0.18 point at the last release in the 0.18 line (0.18.15 from Aug 15)? What does "stable" mean in the context of 0.19 when there seem to be releases every week or so? How is that different than dev?

If those things could be clarified in the API reference and the user guide, that would be very helpful. I'm looking to pin a reasonably stable version for production code, and it would be great if the documentation was available to match that. Thank you for considering!

[stinodego]

dev refers to the latest commit on the main branch, while stable refers to the most recent release.

0.x points to the latest 0.x release, so 0.19 currently points to 0.19.9.

We do not keep docs for every patch version.