Remove the `data-autocomplete-antecedent`, `data-autocomplete-category`,
and `data-autocomplete-post-count` data attributes from the autocomplete
menu. These weren't used by Danbooru itself and they bloat the HTML.
Limit the width of the autocomplete menu to 480px. This is so that
stupidly long isekai titles don't blow out the size of the menu when
searching for common words.
For example, when searching for "look", one of the results is:
no_matter_how_you_look_at_it_it's_your_fault_that_i'm_not_popular! -> watashi_ga_motenai_no_wa_dou_kangaetemo_omaera_ga_warui!
Highlight the matching part of the tag in the autocomplete menu. For
example, if you search "hair", then the word "hair" will be bolded in
every matching tag. This is so users can tell why a particular tag was
matched.
Render the HTML for autocomplete results server-side instead of in
Javascript. This is cleaner than building HTML in Javascript, but it may
hurt caching because the HTTP responses are larger.
Fixes#4698: user autocomplete contains links to /posts
Also fixes a bug where tag counts in the autocomplete menu were different
from tag counts displayed elsewhere because of differences in rounding.
