this adds all subsections and their contents to index.html; it also
disables pagination, since that doesn't seem to work too nicely
with anything more than just a single flat list …
Note that this only goes one level deep — if we ever have subsections of
subsections these currently won't show up in the main index.html.
idea: write markdown, get a more-or-less readable with categories and search
because no one wants to deal with wikis (or just use fd & rg locally, I guess).
Add docs to `content/`; all subdirs of that need a _index.md file that defines
the theme. Categories are just strings and can be defined ad-hoc; the search
goes through all files in `content/` and subdirs based on a search index built
by zola when building the site.
