Added remark about the launcher

README.md

 # traci
 
-Module to interconnect with the traffic simulator SUMO via the traffic control interface (TraCI). 
+Module to interconnect with the traffic simulator SUMO via the traffic control interface (TraCI).
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+
+## SumoLauncher
+
+The `launcher` subdirectory contains a python script that can launch sumo instances on demand
+that can be configured from the code in the ns-3 module. It makes it easier to run multiple
+simulations in parallel or from a scripted environment.