Add realsense docker module and include examples

docs/docker-modules/realsense.md

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+# Realsense
+
+[![GitHub code](https://img.shields.io/badge/code-blue?logo=github&label=github)](https://github.com/j3soon/ros2-essentials/blob/main/docker_modules/install_cartographer.sh)
+
+ROS2 Realsense. (Only installed by default for the template workspace.)
+
+To enable Realsense, set the `REALSENSE` argument to `YES` in the `compose.yaml` file of your desired workspace (e.g., `husky_ws/docker/compose.yaml`). After making these changes, rebuild the Docker image.
+
+> TODO: Remove duplicate content from the template workspace below.
+
+## 🐳 Start Container
+
+> Make sure your system meets the [system requirements](https://j3soon.github.io/ros2-essentials/#system-requirements) and have followed the [setup instructions](https://j3soon.github.io/ros2-essentials/#setup) before using this workspace.
+
+Run the following commands in a Ubuntu desktop environment. If you are using a remote server, make sure you're using a terminal within a remote desktop session (e.g., VNC) instead of SSH (i.e., don't use `ssh -X` or `ssh -Y`).
+
+```sh
+cd ~/ros2-essentials/template_ws/docker
+docker compose build
+xhost +local:docker
+docker compose up -d
+# The initial build will take a while, please wait patiently.
+```
+
+> If your user's UID is `1000`, you may replace the `docker compose build` command with `docker compose pull`.
+
+The commands in the following sections assume that you are inside the Docker container:
+
+```sh
+# in a new terminal
+docker exec -it ros2-template-ws bash
+```
+
+If the initial build somehow failed, run:
+
+```sh
+rm -r build install
+colcon build --symlink-install
+```
+
+Once you have finished testing, you can stop and remove the container with:
+
+```sh
+docker compose down
+```
+
+## Realsense test with gazebo
+
+- realsense_desp package: Description of a robot with realsense D435 camera.
+- realsense_gazebo package: Gazebo simulation of the robot with robot state publisher.
+- Launch Gazebo with turtlebot3 in `tmux`
+  ```bash
+  ros2 launch realsense_gazebo realsense_gazebo.launch.py
+  ```
+
+- Run the control tool in new window of `tmux`
+  ```bash
+  ros2 run rqt_robot_steering rqt_robot_steering
+  ```
+
+## Realsense test in realworld
+
+- Launch Realsense camera node in `tmux`
+    ```bash
+    # add pointcloud.enable:=true to enable pointcloud
+    ros2 launch realsense2_camera rs_launch.py
+    ```
+
+- Open RViz to verify the camera topics in `tmux`
+    ```bash
+    ros2 run rviz2 rviz2
+    ```
+
+## References
+
+- [Realsense ROS Wrapper](https://github.com/IntelRealSense/realsense-ros)
+- [RealSense Gazebo ROS Plugin](https://github.com/pal-robotics/realsense_gazebo_plugin)