Add keyCode signal for keydown events

[justinwoo]

This commit adds a signal for keyCodes from the keydown event to the exports.

Currently, presses are exposed, but they don't capture keyboard arrow key inputs. This makes the natural "key-repeat" keydown events unusable unless one either sets up a port or writes their own Native function, but that would be wasteful since the keydown event is already listened to in the core Keyboard module.

[jvoigtlaender]

You'd have to add "downs" to the @docs section as well, or the package won't be publishable. Also, https://github.com/elm-lang/core/pull/463, though probably they don't interfere.

[jvoigtlaender]

You'd have to add "downs" to the @docs section as well, or the package won't be publishable. Also, https://github.com/elm-lang/core/pull/463, though probably they don't interfere.

[justinwoo]

Ah, thanks.

I think the diff should go through fine with no conflicts, but I could rebase if that one goes in first.

[justinwoo]

Ah, thanks.

I think the diff should go through fine with no conflicts, but I could rebase if that one goes in first.

[evancz]

With 0.17 this is no longer the responsibility of core.

[evancz]

With 0.17 this is no longer the responsibility of core.