Resolve broken links in new docs site

[mfranzke]

Additionally to the changes out of #1153 there are some more links included in the several different files of the repo (.md, .js etc.) as comments or within these documentation files, that would additionally need to get changed.

Please find the list of links within the related PR #1193

Maybe additionally setting up redirects for the old docs pages urls to the new ones might be in general a good idea, as some pages out of the WWW could still be linking to those old URLs. This ticket at least solves the topic of the links within the PL code ecosystem itself.