Allow for searching the help dialog

[oakrotka]

Checklist

• [x] I've looked through the documentation and existing open issues for similar feature requests.

Describe the feature request

Make the / key enter a search state when in a help dialog, where you could search through the help for a keyword.

[ClementTsang]

Can look into doing this!

[cool-RR]

I also found myself wanting this today.