Feature Brei hook and Quarto attributes

[jhidding]

For an example of what you can do with this: see https://entangled.github.io/example-brei

Other minor updates:

• Adds a few languages
• Warns against unknown languages
• Tries to fix the logging situation once more
• Update construct.py to Brei's version

Also: I think after this we can release 2.0 proper.

[jhidding]

I'll merge anyway... sorry for my impatience ;)