Build and deploy with mkdocs on Github Pages

[nilsnolde]

I think it'd be worth the effort bcs:

• much nicer to look at than our home-baked stuff in Wordpress
• much faster to render
• much easier to maintain, I could ditch that WordPress plugin possibly

One clear disadvantage will be that we "lose track" of visited pages. Not that we're obsessing over those stats, but they are very useful.

[nilsnolde]

Actually a more severe disadvantage would be, that it's not directly supported to create a custom menu, at least with the material theme. But need to verify that there's no workaround. It seems a menu (tabs really) is an alternative to the sidebar for the navigation. At least FastAPI seems to have some header component with promotions: https://fastapi.tiangolo.com/ with the same theme. I hope that's not too hacky, will have a look soon, it might serve to overcome that concern.