thank you for your great package.

Just a question.
I know that pluginmux has an ability to add a callback before switching plugin.
But there is no api for the user of 'locomotor' library to add some hooks before switching local planner,
because setSwitchCallback is called inside constructor and local_planner_mux_ is protected.
https://github.com/locusrobotics/robot_navigation/blob/master/locomotor/src/locomotor.cpp#L65

Is it correct to create a new class which inherets 'Locomotor' to achieve that?