Fix lychee link errors

[zastrowm]

Description

Update lychee configuration to match latest CLI behavior (they recently updated things a bit which broke our workflows) & update links that were incorrect (lychee was helping!)

I think before this, it wasn't correctly parsing our files' relative links, leading to lychee not catching things that it should.

The previous successful build before lychee broke us:

Now it's checking even more files and succeeding:

It's also interesting to note that it's reporting a lot of redirects - I'm not doing anything about those right now.

Type of Change

• Bug fix

Checklist

• I have read the CONTRIBUTING document
• My changes follow the project's documentation style
• I have tested the documentation locally using mkdocs serve
• Links in the documentation are valid and working
• Images/diagrams are properly sized and formatted
• All new and existing tests pass

Additional Notes

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