Improving API search

[unlessgames]

While this also relates to the mdbook parts that come into play outside this module, I thought it might be better to keep this issue here as it relates to pretty much any lua api doc you'd want to generate.

There are a couple of issues with the search, some might need fixing here:

• search is limited to 30, this is not enough for big API results (for example searching for visible on the xrnx repo will be flooded with Views links, and visible_note_columns won't make it), this can be bumped easily in the mdbook config using limit-results in [html.output.search]
• the order of search results could be better (xrnx docs again, searching visible_ returns functions where an argument name is matching before matching properties). Ideally the order would look something like class > property/function > arguments > description
• some things are simply not being found, maybe something to do with code-blocks not being searched mid-word? (xrnx docs again, searching DocumentList doesn't return this class at all, but Document.DocumentList does)

[unlessgames]

• search result will not always take you to the actual subsection, for example search for undo in the xrnx repo, click the link that points to Song.undo(), it will take you to the Song class but not the undo function. The generated url hash is #undo--self-- which won't work while just #undo would. Maybe an issue with italic formatting of self in the signature?

[emuell]

I don't really have time for this, and I don't think it's a particularly stressful feature. But, if you have the time and you think it's important, please feel free to take over.

[unlessgames]

I agree it's not the end of the world but if the fix is simple it might worth it. mdbook does allow for swapping the search functionality for a custom implementation, I'll check how difficult it would be to make use of that here.