UX: launch full page search on second `Enter` hit (PR #14978)

When using the quick search, a second hit of the Enter key should launch the full page search. This is useful now that topic/post results require hitting Enter. To ensure this doesn’t cause any unwanted redirects, this only applies as long as the first press of the Enter key happened no more than 15 seconds ago.

This PR also adds a keyboard shortcut entry in the help modal for Ctrl + Enter, which also launches full page search.


nice, many people mentioned that they miss this, keen to try it out.