Add readme for gamepad unit

source/RobotAPI/drivers/GamepadUnit/README.md

+# GamepadUnit
+
+This component is used to control the robot with a gamepad.
+
+You have to set two device names:
+ - `GamepadDeviceName`
+   - Used to read the input from the device.
+    You can find the proper name by checking various names from `/dev/input/js*` with the command line util `jstest`.
+ - `GamepadForceFeedbackName`
+   - Used to give force feedback on the controller.
+    You can find the proper name by checking various names from `/dev/input/event*` with the command line util `fftest` or `evtest`.
+
+Alternatively you can find the proper name through `/dev/input/by-id`.
+
+E.g. for a Logitech F710 gamepad the proper names are: \
+`GamepadDeviceName=/dev/input/by-id/usb-Logitech_Wireless_Gamepad_F710_582F9A6B-joystick` \
+`GamepadForceFeedbackName=/dev/input/by-id/usb-Logitech_Wireless_Gamepad_F710_582F9A6B-event-joystick`