I have no idea how the option to search the forum works, but could it be a thing in the docs, too? Because that would be AWESOME!
I think it already exists... the main doc page has a 'search bar' that I think uses the google custom search (same as the forum), I think:
http://docs.textadventures.co.uk/quest/ (right at the top, in the 'contents' section, at the bottom, below the 'contributing' link is the 'search' link, which is right above the 'tutorial' section too. Also, at the very bottom of the main doc page is a 'google custom search' search bar, as well)
I think it already exists...
Ha! It does!
(I didn't see that little sucker way down there...)