Added MRSLAM gif showing mapping and loop closure

Author: jsongCMU

README.md

@@ -46,6 +46,10 @@ The video below was collected at [Circuit Launch](https://www.circuitlaunch.com/
 
 ![map_image](/images/circuit_launch.gif?raw=true "Map Image")
 
+# Multi-Robot SLAM
+SLAM Toolbox now supports multi-robot SLAM. The robots must all start in the same location, facing the same way; this way, they can determine relative positions at startup, and use this information to build upon a shared pose graph. This allows localization of multiple robots, mapping using information from all sensor readings, and loop closures across robots. Currently, synchornous and asynchornous mapping is supported.
+
+![MRSLAM_gif](/images/mrslam_readme.gif?raw=true "Multi-Robot SLAM")
 
 # 03/23/2021 Note On Serialized Files