Update readme for Noetic

README.md

@@ -55,7 +55,7 @@ We design a system that maintains two graphs and runs up to 10x faster than real
 
 This is the original ROS1 implementation of LIO-SAM. For a ROS2 implementation see branch `ros2`.
 
-- [ROS](http://wiki.ros.org/ROS/Installation) (tested with Kinetic and Melodic)
+- [ROS](http://wiki.ros.org/ROS/Installation) (tested with Kinetic and Melodic. Refer to [#206](https://github.com/TixiaoShan/LIO-SAM/issues/206) for Noetic)
   ```
   sudo apt-get install -y ros-kinetic-navigation
   sudo apt-get install -y ros-kinetic-robot-localization