message: Group struct docs
diff: @@ -148,6 +148,10 @@ public:
  * (https://github.com/PX4/Firmware/blob/v1.9.0/src/modules/mavlink/mavlink_receiver.cpp#L980).
  */
  struct ActuatorControl {
  + /**
  + * @brief Eight controls that will be given to the group. Each control is a normalized
  + * (-1..+1) command value, which will be mapped and scaled through the mixer.
  + */
  struct Group {
  float controls[8]; /**< @brief Controls in the group. */
  };
  