add more documentation to the InterfacesValues msg

Author: saikishor

control_msgs/msg/InterfacesValues.msg

@@ -1,4 +1,13 @@
 std_msgs/Header header
 
 # List of values corresponding to the interfaces or joints defined in InterfacesNames.msg
+# The size and order must match that of InterfacesNames.msg
+# Each value corresponds to the name at the same index in InterfacesNames.msg
+#
+# For example. if InterfacesNames.msg has names = ["joint1/position", "joint2/velocity"], then
+# InterfacesValues.msg could have values = [1.57, 0.0]. The first value (1.57) corresponds to "joint1/position"
+# and the second value (0.0) corresponds to "joint2/velocity"
+#
+# This message is used by the interfaces_state_broadcaster to publish the values of the interfaces via
+# ROS2 topics ~/names (InterfacesNames.msg) and ~/values (InterfacesValues.msg)
 float64[] values