Allow interaction with olympus through controller

[Feature Request]

Since Celeste is a platformer game, quite a couple of players are on controller. It personally bothers me a bit when there is an update or some other reason why I have to open olympus and I have to put my controller down and start using my mouse and keyboard again. So I think controller input like in steam big picture mode for example, would be really nice!

Start by reviewing Olympus's current input handling and interface flow, then compare the requested behavior with controller navigation in Steam Big Picture mode. Done means users can perform Olympus interactions after updates or other launches using a controller without switching to a mouse and keyboard.

Written by the indexing model from the issue text.