Support of other Robot Platforms

[msminirobot]

To support other robot sdf files, you can switch to the following code in src/driving_swarm_bringup/driving_swarm_bringup/nav2_gazebo_spawner.py, lines 70-75:

    for plugin in root.iter('plugin'):
        if 'libgazebo_ros_diff_drive.so' in plugin.attrib.values():
            break 

(Tested for AgileX Limo)