Publish robot description in environment monitor

[marip8]

In ROS2, various nodes (namely the joint state publisher and joint state publisher GUI) listen to the robot_description parameter for the URDF before they start working. If you want to use the environment monitor as the source of TF rather than the robot state publisher, then it needs to publish the robot description for these nodes. It should also probably re-publish the URDF if structural changes are made to the environment (e.g., addition of new actuated joints, etc.)