Make quick jump more discoverable with visible search bar

[sullyj3]

Hey there! First of all, this is a fantastic project, I really appreciate the work you guys do.

I have a feature request regarding the quick jump functionality. Unfortunately it's not very discoverable. It took me a long time to find out about it, and there's another example of someone who was unaware of it in this thread. This is the kind of papercut that can easily lead to frustration with haskell newcomers.

Compare rustdoc, which has a prominent search bar at the top, exposing this functionality, together with a tip about the 's' keyboard shortcut. In my opinion, haddock ought to display something similar to this.

Hopefully this is a feature the project can get behind! I'm interested to hear people's thoughts.