Add documentation for curiosity_rover demos

related to space-ros/space-ros#178

 - Add README.md for Curiosity Rover demo
 - Update Main README.md of the demos repository

README.md

@@ -2,4 +2,6 @@
 
 This repository provides examples for running robots using Space ROS
 
-Please refer to the [dockerfile repo](https://github.com/space-ros/docker/tree/main/space_robots) for running instruction
+## Demos
+
+1. [Curiosity Rover](curiosity_rover/README.md)

curiosity_rover/README.md

@@ -0,0 +1,70 @@
+# Curiosity Rover - Demo
+
+This is a simple demo of controlling the curiosity rover using spaceROS.
+
+### Installation
+
+To start the demo, there are few dependencies that need to be installed. The following steps will guide you through the installation process.
+
+1. You will need ROS Humble on your host system. If it is not already installed, you can follow the instructions [here](https://docs.ros.org/en/humble/Installation.html).
+2. You will need Gazebo Sim installed on your system. If not, you can follow the instructions [here](https://gazebosim.org/docs/all/getstarted/).
+3. You will need docker installed on your system. If not, you can follow the instructions [here](https://docs.docker.com/get-docker/).
+4. Install xterm for running the demo. You can install it using the following command.
+    ```bash
+    sudo apt-get install xterm
+    ```
+
+### How to run the demo
+
+1. Clone the demo repository
+    ```bash
+    git clone http://github.com/space-ros/demo.git
+    ```
+2. cd into the `curiosity_rover` directory
+    ```bash
+    cd curiosity_rover
+    ```
+3. To build and run the demo, we use `Makefile`. Run the following command to build the docker image and run the container.
+    ```bash
+    # To see the list of available commands
+    make help
+
+    # To build and run the demo
+    make run
+    ```
+
+This will start the demo in one terminal and gazebo in another terminal. To control the rover, we provide ros2 services for the demo. You can control the rover using the following services.
+
+1. To move around, you can use the `move` service. The service takes two arguments, `linear` and `angular` velocities. You can call the service using the following command.
+    ```bash
+    # Move forward
+    ros2 service call /move_forward std_srvs/srv/Empty "{}"
+
+    # Turn left
+    ros2 service call /turn_left std_srvs/srv/Empty "{}"
+
+    # Turn right
+    ros2 service call /turn_right std_srvs/srv/Empty "{}"
+
+    # Stop
+    ros2 service call /stop std_srvs/srv/Empty "{}"
+    ```
+2. To control the arm of the rover, you can run the following services,
+    ```bash
+    # Open the arm
+    ros2 service call /open_arm std_srvs/srv/Empty "{}"
+
+    # Close the arm
+    ros2 service call /close_arm std_srvs/srv/Empty "{}"
+    ```
+3. To control the mast arm of the rover, you can run the following services,
+    ```bash
+    # Open the mast arm
+    ros2 service call /mast_open std_srvs/srv/Empty "{}"
+
+    # Close the mast arm
+    ros2 service call /mast_close std_srvs/srv/Empty "{}"
+
+    # To rotate the mast arm
+    ros2 service call /mast_rotate std_srvs/srv/Empty "{}"
+    ```