message: Add gimbal, follow_me and logging to API list in README
diff: @@ -41,10 +41,14 @@ The links below take you to the respective header files:
  - [telemetry](plugins/telemetry/telemetry.h): to receive telemetry data
  - [action](plugins/action/action.h): to send commands such as arm, disarm, takeoff, land to drone
  - [mission](plugins/mission/mission.h)/[mission_item](plugins/mission/mission_item.h): to upload a waypoint mission
  -- [offboard](plugins/offboard/offboard.h): for velocity or position control
  +- [offboard](plugins/offboard/offboard.h): for velocity control
  +- [gimbal](plugins/gimbal/gimbal.h): control a gimbal
  +- [follow_me](plugins/follow_me/follow_me.h): drone tracks a position supplied by DroneCore.
  +- [logging](plugins/logging/logging.h): (not implemented) data logging and streaming from the vehicle.
  For more information see the [API Overview](https://docs.dronecore.io/en/getting_started/#api-overview) in the DroneCore Guide.
  +
  ## Guide Docs (Build instructions etc.)
  Instructions for how to use the library can be found in the [DroneCore Guide](https://docs.dronecore.io/en/).
  