Gets the value of a button based on the given index. The index must be valid within the range of buttons supported by this Gamepad.
The return value will be either 0 or 1 for an analogue button, or a float between 0 and 1 for a pressure-sensitive digital button, such as the shoulder buttons on a Dual Shock.
The index of the button to get the value for.
The value of the button, between 0 and 1.