Add ROS Melodic wiki link

README.md

@@ -19,7 +19,7 @@ instructions further below in this document. Please note that the setup uses vnc
 ## Requirements for development
 
 - Ubuntu 18.4
-- ROS Melodic
+- ROS Melodic (http://wiki.ros.org/melodic/Installation/Ubuntu)
   - *additionally required packages:* `ros-melodic-libfranka` `python-catkin-tools` `libeigen3-dev`
 
 ## Installation