Doc search can bring up docs for out-of-date versions

[a10y]

Docs search seems to retrieve pages from all versions by default. Since many pages are duplicated across versions, it'd be easier to find things if search only went over the most recent major version, or if the version were selectable.

E.g. I was looking up docs for logging integration. I eventually found this page, but my first few results were for a page from 0.5