Tweak search rankings in documentation

[pokey]

Currently, if you search for "copy" in the cursorless docs, the top results are all from the contributor side, rather than the user documentation for the "copy" action. In addition, the top-level sections in the search box are strange, with "For users" being on the same level as subsections of "For contributors", such as "Classes" and "Interfaces":

We'd like to do the following:

• [ ] Prioritise the user docs, especially if the user is currently in the user docs
• [ ] Change the hierarchy so that "For users" and "For contributors" are the top levels of the hierarchy

This issue does beg the question of whether we want to have a harder separation between user docs and contributor docs