Gazebo: add doc for BlueBoat

Signed-off-by: Rhys Mainwaring <[email protected]>

Gazebo/docs/BlueBoat.md

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+# BlueBoat
+
+[Blue Robotics BlueBoat](https://bluerobotics.com/product-category/boat/) (operates as [skid steer rover](https://ardupilot.org/rover/docs/rover-motor-and-servo-configuration.html#skid-steering) in ArduPilot using
+the [Boat](https://ardupilot.org/rover/docs/boat-configuration.html#boat-configuration) `FRAME_CLASS`).
+
+![blueboat_gz](https://github.com/ArduPilot/SITL_Models/assets/24916364/11213e94-9e58-45eb-8181-1cec6c64ee19)
+
+## Usage
+
+Gazebo and the plugins should be installed as per the [ArduPilot Gazebo Plugin](https://github.com/ArduPilot/ardupilot_gazebo) instructions.
+
+Update the `GZ_SIM_RESOURCE_PATH` to include these models:
+
+```bash
+export GZ_SIM_RESOURCE_PATH=$GZ_SIM_RESOURCE_PATH:\
+$HOME/SITL_Models/Gazebo/models:\
+$HOME/SITL_Models/Gazebo/worlds
+```
+
+#### Waves model
+
+The model is configured to work with the hydrodynamics plugin from the [wave sim](https://github.com/srmainwaring/asv_wave_sim) package. Follow the package instructions to set up the marine simulation.
+
+The model may be included in the [`waves.sdf`](https://github.com/srmainwaring/asv_wave_sim/blob/master/gz-waves-models/worlds/waves.sdf) world by adding the element:
+
+```xml
+<include>
+  <pose degrees="true">0 0 0 0 0 90</pose>
+  <uri>model://blueboat</uri>
+</include>
+```
+
+#### Run Gazebo
+
+```bash
+gz sim -v4 -r waves.sdf
+```
+
+#### Run ArduPilot SITL
+
+```bash
+sim_vehicle.py -D -v Rover -f rover-skid --model JSON  --console --map
+```
+
+The default skid steer rover parameters give a workable simulation with minor modifications:
+
+```bash
+CRUISE_SPEED      2.0
+CRUISE_THROTTLE   50.0
+FRAME_CLASS       2.0
+WP_SPEED          2.0
+```
+
+![blueboat_gz_clip](https://github.com/ArduPilot/SITL_Models/assets/24916364/c2fb9c7f-bde2-46ba-9a3a-e4e641163b67)
+
+## Notes
+
+The hull form used to model the hydrodynamics is an approximation. It has slightly more volume in the keel fins and aft, which requires the centre of mass in the simulation to be moved aft for level trim. The hull collision meshes used to calculate the buoyancy and hydrodynamics could be further refined to more closely model the true hull form at a later stage if needed.
+
+<img width="1312" alt="blueboat_gz_waterline" src="https://github.com/ArduPilot/SITL_Models/assets/24916364/4e1f9a2d-85d3-4ab7-91a7-6606a4b11727">
+
+
+## Credits
+
+Original 3D Models retrieved from BlueRobotics: [BLUEBOAT_120_BR-101447_RevA_PUB](https://cad.bluerobotics.com/BLUEBOAT_120_BR-101447_RevA_PUB.zip)