Add link to list of commands.

[MichelleGlauser]

For the MVP, we don't need a hint to show up when the wrong keys are pressed. Let's just have the input field turn red and supply a constant link to a list of commands people can refer to.

[vegetabill]

@MichelleGlauser the correct keys are already highlighted so I'm thinking we don't need this after all. But please reopen if we want to have different behavior, such as toggle-able hints in #4