Merge pull request #1375 from SteveMacenski/diagram

adding navigation2 new diagram

README.md

@@ -13,6 +13,8 @@ ROS2 Navigation System
 # Overview
 The ROS 2 Navigation System is the control system that enables a robot to autonomously reach a goal state, such as a specific position and orientation relative to a specific map. Given a current pose, a map, and a goal, such as a destination pose, the navigation system generates a plan to reach the goal, and outputs commands to autonomously drive the robot, respecting any safety constraints and avoiding obstacles encountered along the way.
 
+![nav2_overview](doc/architecture/navigation_overview.png)
+
 # Documentation
 For detailed instructions on how to install and run the examples, please visit our [documentation site](https://ros-planning.github.io/navigation2/).