Unify keyboard events on docs.rs results

[GuillaumeGomez]

Reopening of #1452.

The keyboard events are suboptimal currently. So I improved them a bit by following what @jsha did in rustdoc. It allows to also centralize the JS in one file and remove the inline JS we currently have. Small demo below:

Peek.2021-07-20.17-26.mp4

So what it does:

• Pressing 'S' will focus the search input (in both home page and docs.rs search result pages).
• No event are handled in the search input (thinking about the key arrows). This is to prevent impacting accessibility.
• If no element is focused or if a search result is focused, up/down arrows will go through the search results by setting the current one as the "active element".
• Pressing 'esc' will blur the current active element (including the search input).

cc @Manishearth @jsha

[GuillaumeGomez]

cc @jsha since it's very close to what you did in rustdoc search. :)

[jsha]

Could you provide a browseable demo? I don't currently have an up-to-date docs.rs env set up on my machine. I can get that working again but it might take a little while.

Also, can you confirm: This is not supposed to add new functionality, just rearrange code, right?

[GuillaumeGomez]

I unfortunately can't, my server doesn't allow me to serve URLs with binaries... :-/

I think someone else nicely provided PRs like that. Was it you @Nemo157 by any chance?

Also, can you confirm: This is not supposed to add new functionality, just rearrange code, right?

Unification to be exact. I merge functionalities from 2 different pages. With this PR, we can now go through listed crates using arrows and on the search page we can focus on the search input using 'S'.

[jsha]

Generally looks good to me. One meaningful typo and one small tweak.

Note that I'm not an approver on this repo so you'll need a second review from someone who is.

[GuillaumeGomez]

Thanks @jsha for the review! It made me realize that it wasn't great so I simplified it a bit (making the code a bit longer) and added comments so it's easier to follow. Hopefully this should be much better now.

[jsha]

Looks good to me.