Additional CI/CD features

[k4kfh]

This repo would benefit from a number of additional CI/CD features. Including:

• Automatic link-checking, at least for PRs, with something like this: https://github.com/marketplace/actions/check-links-with-linkcheck
• Build PDF docs using LaTEX for a pull request (ReadTheDocs does not do this for PR builds)
• Check that no content extends into the margins on PDF and EPUB outputs. Since ReadTheDocs does not generate these formats automatically for PRs, and a large LaTEX toolchain is required to generate them locally, this is a difficult issue to review. Tables are particularly bad about doing this in the PDF output.
• Automatic spell-checking, at least for PRs
• "Edit on GitHub" feature on each page, for quick minor edits/PRs done directly in the browser. I want to make it as easy as possible for non-Git-users to contribute quick fixes/docs improvements.
• Automatic generation of a "Contributors" page, to be used in all output formats (PDF, HTML, EPUB)
• Automatically build .drawio diagrams into PNG or JPG images. Or find another way to integrate these diagrams more neatly into Sphinx (I don't know if the direct Draw.io plugins for Sphinx are stable with PDF/EPUB outputs, so I would tend to think that exporting to an image and using the figure Markdown directive is still our best bet).

I can't focus on this right now because getting updated content written is more important, and I'm not that good at CI/CD anyway. But if somebody else wants to help out, I'd appreciate it.

[ra3xdh]

This could be implemented in the future. Let's concentrate on documentation itself in the moment.

[k4kfh]

I completely agree, I just thought having an issue open to capture the idea might be helpful. But if you think it's a distraction to have the issue sitting around, I'm happy to close it and limit issues to only what should be done immediately.