Include 2D Navigation Goals link.

README.md

@@ -34,3 +34,4 @@ To help get you get started on your software development, here are examples of n
 10. [Tf2 Broadcaster and Listener](example_10.md) - Create a tf2 broadcaster and listener.
 11. [PointCloud Transformation](example_11.md) - Convert PointCloud2 data to a PointCloud and transform to a different frame.
 12. [ArUco Tag Locator](example_12.md) - Actuate the head to locate a requested ArUco marker tag and return a transform.
+13. [2D Navigation Goals](example_13.md) - Send 2D navigation goals to the move_base ROS node.