Add node on namespaces.

canopen_tests/ROS_NAMESPACES.md

@@ -0,0 +1,11 @@
+The `cia402_namespaced_system.launch.py` example demonstrates how to run a 
+CIA402 system in a namespace to allow multiple CANOpen-based robots in the 
+same ROS domain. This example is neccessary because the controller names
+are picked up from `ros2_controllers.yaml` and we must define their names
+in that file with a `__namespace__/controller_name:` key, then use
+ReplaceString from `nav2_common` to dynamically add the namespace to the
+controller definition.
+
+For a proxy system, no example is included; it's sufficient to include, e.g.
+the `proxy_setup.launch.py` launch description in another launch file and
+push a namespace onto it with PushROSNamespace in the ordinary way.