Check links in docs

[bmschmidt]

Many, it has been reported, return a 404.

[organisciak]

Have you tried compiling the HTML from my last commit to API.md in d532cd0?

[organisciak]

I did a quick search for "](githu" and API.md was the only place with the relative links, though it's probably better to search for any links that don't start with https. And "bmschmidt" needs to change to Bookworm-project in some links.

I feel rude just giving instruction rather than fixing it, but rushing out to an appointment right now.