Improve navigation of top-level sections

[bast]

These pages are now automatically generated:

• https://coderefinery.org/lessons/
• https://coderefinery.org/workshops/
• https://coderefinery.org/join/
• https://coderefinery.org/about/

Problems:

• The order does not match the order in menus
• Some pages do not have a description
• Not sure all pages even show up (example: https://coderefinery.org/about/reports/)

[bast]

The same mechanism/source should generate the main navigation and the page-navigations.

[bast]

I now know more about Zola than earlier and I think I can fix this in a good way.