minor release history change

docs/md_files/release_history.md

@@ -4,8 +4,15 @@ This page demonstrates all the changes since the origin release v0.1.0 with more
 --- 
 ### v0.1.2
 ##### Map manager
-OpenCDA now adds a new component `map_manager` for each cav. It will dynamically load road topology and dynamic
+OpenCDA now adds a new component `map_manager` for each cav. It will dynamically load road topology, traffic light information, and dynamic
 objects information around the ego vehicle and save them into rasterized map, which can be useful for RL planning, HDMap learning, scene understanding, etc.
+Key elements in the rasterization map:
+- Drivable space colored by black
+- Lanes
+  - Red lane: the lanes that are controlled by red traffic light
+  - Green lane: the lanes that are controlled by green traffic light
+  - Yellow lane: the lanes that are not effected by any traffic light
+- Objects that are colored by white and represented as rectangle
 
 ![](images/map_manager.gif )