Convert recipe examples to includes

Makes it much easier to test things - no copying'n'pasting just run the
examples straight from the dir (after wiring stuff up)

docs/examples/robot_keyboard_2.py

@@ -0,0 +1,21 @@
+from gpiozero import Robot
+from evdev import InputDevice, list_devices, ecodes
+
+robot = Robot(left=(4, 14), right=(17, 18))
+
+devices = [InputDevice(device) for device in list_devices()]
+keyboard = devices[0]  # this may vary
+
+keypress_actions = {
+    ecodes.KEY_UP: robot.forward,
+    ecodes.KEY_DOWN: robot.backward,
+    ecodes.KEY_LEFT: robot.left,
+    ecodes.KEY_RIGHT: robot.right,
+}
+
+for event in keyboard.read_loop():
+    if event.type == ecodes.EV_KEY:
+        if event.value == 1:  # key down
+            keypress_actions[event.code]()
+        if event.value == 0:  # key up
+            robot.stop()