[rustdoc] Add a marker to tell users that there are hidden (deprecated) items in the search results
Someone on mastodon rightfully pointed out that having a visual indication that some search results were hidden would be a good idea if the "hide deprecated items" setting is enabled. In particular if no results are displayed.
It looks like this:
<img width="861" height="228" alt="Screenshot From 2026-01-24 00-26-33" src="https://github.com/user-attachments/assets/93aeef11-a550-47dc-9c78-219ea4fd822c" />
r? @lolbinarycat
f5822b672b