Update GitHub docs

[martinjohndyer]

Fix two outstanding errors with the auto-generated docs at https://hipercam.github.io/hipercam:

• Ensure the version number is correctly displayed at the top of every page (7f400a3)
• Automatically include the script documentation in the Commands page (done by replacing sphinx-autodoc with sphinx-autoapi, 76789ac)

I also fixed a handful of warnings to do with typos in formatting that showed up in the Sphinx logs.

Once this is merged, and for every change to the repository form now on, GitHub Actions should rebuild the docs and update https://hipercam.github.io/hipercam automatically. We can then use that as the one true source of the pipeline documentation (#149).

Note https://hipercam.github.io currently doesn't exist, I'll look at putting a basic landing page or redirect there since it's a little easier for people to remember.