Expand out Engine::_glfwKeyCallback #15
Description
Currently, it only supports backspace, left, right, delete, end, and home.
Also, the way it handles events are a bit strange, and are not very expandable.
whenever an input event is propagated to the listeners
we could just pass along the current state of the modifier keys
and let whichever part that requires them to handle it on its own
Still keep the system of requesting key inputs to prevent lag on key events, but allow for better support with custom classes.