ENH: add search box

[bsipocz]

Please describe the new feature.

Is this intentional that there isn't a search box on the site?

(I was doing triage for the currently open issues as was not able to just look for stuff on the website without looking into PRs/the content from the repo)

Add any other context about the new feature here, screenshots, etc.

No response

[stefanv]

There's a PR on the theme to add search, but it hasn't been merged yet.