[ docs ] Update look 'n feel

[jfdm]

Traditionally, Sphinx required authors to use reST and provided basic markdown support. Now, myST is a variant of markdown that incorporates many reST features but in a markdown many are familiar with.

This PR does the following:

1. Introduce myST as a dependency, enabling authors to use myST for input;
2. Change the style to sphinx-book-theme a more featured html style that enables more featured documentation to be written.
   Including, light/dark modes.
3. Pull in bibtex tooling and 'copy button' for code.
4. Provide instructions for managing python projects using the uv tool.

Description

Self-check

• This is my first time contributing, I've carefully read CONTRIBUTING.md
  and I've updated CONTRIBUTORS.md with my name.
• If this is a fix, user-facing change, a compiler change, or a new paper
  implementation, I have updated CHANGELOG_NEXT.md

[jfdm]

I will update the changelog later.

[gallais]

Do you know if there's anywhere we can see the rendered result?

Files like uv.lock seem autogenerated (unless you're the SHA master who can see
through them like through matrix code :D); should we document how/when to
regenerate them or are we not expecting them to change?

[jfdm]

Do you know if there's anywhere we can see the rendered result?

urgh, I thought there would be something from my github. Alas no.

So I have dumped something temporary here

Files like uv.lock seem autogenerated (unless you're the SHA master who can see
through them like through matrix code :D); should we document how/when to
regenerate them or are we not expecting them to change?

We can add a note. For uv, the lock file is generated automatically when uv is invoked.