This does not yet follow #701, because the change to get there would be
too big. The goal is to keep the table of contents meaningful at all
times and the diff of each pull request manageable.
The packaging tutorial is quite important, so it's not wrong to have it
visible on the front page until we have enough material for a packaging
section.
The sharing dependencies article should really be a very brief guide, but
because that would be quite a big change, it's only moved to the Guides
section for now.
* add Recipes section under Guides category
This also removes the templates section, as we're not maintaining it and it likely won't be necessary anyway once the curriculum is roughly finished.
