event module contains traits and structs to actually run your game mainloop
and handle top-level state, as well as handle input events such as keyboard
A trait defining event callbacks; your primary interface with
ggez's event loop. Have a type implement this trait and
override at least the update() and draw() methods, then pass it to
event::run() to run the game's mainloop.
Runs the game's main loop, calling event callbacks on the given state
object as events occur.