Update README.rst to include Gamepad info.

Author: dhalbert

README.rst

@@ -136,6 +136,22 @@ remote controls, or the multimedia keys on certain keyboards.
     # Pause or resume playback.
     cc.send(ConsumerControlCode.PLAY_PAUSE)
 
+The ``Gamepad`` class emulates a two-joystick gamepad with 16 buttons.
+
+*New in CircuitPython 3.0.*
+
+.. code-block:: python
+
+    from adafruit_hid.gamepad import Gamepad
+
+    gp = Gamepad()
+
+    # Click gamepad buttons.
+    gp.click_buttons(1, 7)
+
+    # Move joysticks.
+    gp.move_joysticks(x=2, y=0, z=-20)
+
 Contributing
 ============