Scala3doc/fixes in scaladoc

[romanowski]

Includes:

• Fix rendering of .html files from static pages
• Process links from static documentaiton corrently
• Fix rendering of images on static pages
• Render pages outside sidebar as well
• Add titles in documentation pages
• Update Highlight.js with for common languages

[abgruszecki]

The code for the PR looks good. I've found a problem with resolving links in blogs, though. On the http://localhost:8000/scala3/docs/-reference/-metaprogramming/toc.html page, all the links are broken because they have the wrong suffix - for instance, one link goes to http://localhost:8000/scala3/docs/-reference/-metaprogramming/macros.md when it should go to http://localhost:8000/scala3/docs/-reference/-metaprogramming/macros.html.

There also seems to be an issue with internal padding between border and inner text disappearing for code snippets in blogs posts. I say "disappearing", because when the page first loads the padding is still there, but after a second (possibly after hljs runs?) the padding disappears.

[romanowski]

I've double checked and all links in https://scala3doc.virtuslab.com/pr-master/scala3/docs/-reference/-metaprogramming/toc.html works as expected.