GlobalHotKeys were abandoned, because they were capturing events that
had called stopPropagation. This meant that something needed to be in
focus, hence passing a ref of the HotKey DOM element to the Editor.
react-hotkeys has been updated to 2.0.0-pre9, because 2.0.0 captured
ctrl keypresses when asked for ctrl+enter
Currently only classic challenges can be executed by hotkey, but all
allow hotkey navigation
