Document the keys

[harry-wood]

You didn't describe what the keys are in the README (there isn't some other documentation somewhere hey?)

It's the arrow keys! But in the code I also noticed R and F supposedly move up and down. Playing the game I didn't find anything to move up and down on. Is there ladders or something somewhere? Guess I should've played the original game more!

But more importantly... isn't there a way to get it into the vehicles?