Split the documentation site out from the main website

[ikeycode]

We have the aging docs subdomain running docusaurus. A while ago we merged docs + main website using the docsy theme - but this has severely impacted usability and generally feels less polished.

We need to split the sites again and move all docs back under one doc-specific site. The floor is open in terms of continuing with docusaurus or not.

[ermo]

I don't have a strong opinion re. which tool is used.

I only really care that the process for doing updates and publishing them is as sane as we can reasonably make it, which to me means:

• Make the prerequisites installable via just so the documentation can go "To get started with working on the docs site, run just do-the-thing and you should be able to then build the site locally with (...)."
• Make it easy to generate (and spell-check/vet) site builds from your local branches (this ties into the above point)
• That we can live with the way the end solution looks.

[knolljo]

I can recommend starlight. It builds a static site and is easy to use with many great features.
CachyOS uses it for example: https://wiki.cachyos.org/

The setup is fairly easy, it just needs a js runtime and an editor.