[Proposal] Controller / Keyboard Navigation Hints

[Martin-Pitt]

A common or really useful pattern is on-screen hints for keyboard or controller actions.

This is a simple accessibility pattern that's even used on websites (e.g. for example on the bottom of flickr site while viewing images it tells you what useful keyboard shortcuts are available for navigating around quickly)

If someone wants to pick up and implement this pattern on the site feel free to take over.