write docker setup at readme (ethz-asl#57)

* write docker setup at readme

Co-authored-by: Ryan <ryanfriedman5410+github@gmail.com>

README.md

@@ -26,6 +26,41 @@ Build the package
 ```
 colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release --packages-up-to grid_map_geo
 ```
+## Docker Setup
+
+If your operating system doesn't support ROS 2 humble, docker is a great alternative.
+
+First of all, you have to build the project and create an  image like so:
+
+```bash
+## Assuimg you are in the correct project directory
+docker build -t gmg .
+```
+To use a shortcut, you may use the following command:
+
+```bash
+## Assuimg you are in the correct project directory
+make docker_build
+```
+
+After the image is created, copy and paste the following command to the terminal to run the image:
+
+```bash
+## Assuimg you are in the correct project directory
+docker run -it --net=host --ipc=host --privileged --env="DISPLAY"  --env="QT_X11_NO_MITSHM=1" --volume="/tmp/.X11-unix:/tmp/.X11-unix:rw" --volume="${XAUTHORITY}:/root/.Xauthority"  --entrypoint /bin/bash gmg
+```
+To use a shortcut, you may use following command:
+
+```bash
+make docker_run
+```
+## Running the package at docker image
+
+If you are in the docker image , this project is already sourced and the default launch file can be run as the following command;
+
+```bash
+ros2 launch grid_map_geo load_tif_launch.xml
+```
 
 ## Running the package