message: Add specific comments about the controllers
diff: </class>
  <class name="franka_example_controllers/CartesianImpedanceExampleController" type="franka_example_controllers::CartesianImpedanceExampleController" base_class_type="controller_interface::ControllerBase">
  <description>
  - A controller that renders a spring damper system in cartesian space.
  + A controller that renders a spring damper system in cartesian space. Compliance parameters and the equilibrium pose can be modified online with dynamic reconfigure and an interactive marker respectively.
  </description>
  </class>
  <class name="franka_example_controllers/ForceExampleController" type="franka_example_controllers::ForceExampleController" base_class_type="controller_interface::ControllerBase">
  <description>
  - A controller that applies a feedforward force in the z axis
  + A PI controller that applies a force corresponding to a user-provided desired mass in the z axis. The desired mass value can be modified online with dynamic reconfigure.
  </description>
  </class>
  