Test for dead links in Quarto documentation

[evetion]

I wish Quarto render would error by default, also for external links, but last I checked I didn't see a way to enable that.

But yes, we should look into external tooling for this, feel free to make an issue.

Originally posted by @visr in #1842 (comment)

Ideally it would work on pre-commit.

[Huite]

This one has github a action: https://github.com/lycheeverse/lychee/

[visr]

I tried lychee in c46b0e9 but that wasn't working yet. I think it would work better as part of the doc render pipeline. When the quarto docs are done, run lychee on the HTML file before publishing. At that stage the internal Quarto links like in #1842 should also be checkable. In my commit I didn't get it to trigger on broken links in QMD files.