[CI] Check relative links are correct

[ee7]

Not a priority for now, but it would be nice to have a script that does something like:

• For every markdown file:
  • For every link:
    • If it's a relative link:
      • Check that it resolves to a file in this repo, using the logic that the website uses (no .md extension, etc)
      • Bonus: check that any anchor is correct too

[SaschaMann]

Could probably use Erik's link check tool for this again: https://github.com/exercism/v3/blob/main/.github/workflows/valid-links.yml

[ErikSchierboom]

I've recently found lychee: https://github.com/lycheeverse/lychee This tool is much more full-featured than my tool and a lot faster (it's built in Rust).

[iHiD]

Nice. The challenge here is probably the fact that relative links are relative in the context of the website; the therefore the race-condition of new links being added but not merged, so not appearing in the website.

I feel like we probably need to build out the array of all routes from the config.jsons, and then check against that?

[ErikSchierboom]

Yeah, I think that's probably best

[ee7]

Some actions that we might be able to adapt:

• https://github.com/lycheeverse/lychee-action
• https://github.com/JustinBeckwith/linkinator-action