Change index.ros.org -> docs.ros.org. (#307)

Signed-off-by: Chris Lalancette <[email protected]>

Author: clalancette

README.md

@@ -1,4 +1,4 @@
 ROS 2 examples
 ==============
 
-To see some of these examples in use, visit the ROS 2 Tutorials page: https://index.ros.org/doc/ros2/Tutorials/
+To see some of these examples in use, visit the [ROS 2 Tutorials page](https://docs.ros.org/en/rolling/Tutorials.html).