#DocSearch-HitsFooter doesn't show in Sphinx

Hi, I was expecting `#DocSearch-HitsFooter` to show in my search in my Sphinx doc (`sphinx-book-theme`), but it's missing.

Is there a special setting I need to set for it to show, assuming my theme may be missing "something" that it wants?

Reproduce the missing #DocSearch-HitsFooter with the sphinx-book-theme configuration described in the issue, then inspect how the theme integrates with Sphinx search results. Done means identifying the required setting or confirming that the theme needs support for this element.

Written by the indexing model from the issue text.