Possibly adding a Gateway demo

[ana-GT]

Feature description

A few weeks ago, the Gateway model (.glb) was uploaded in the NASA-3D-Resources github repo. Based on this file, our team created a ROS2 package that allows loading the robot in Rviz and move the joints of any of the 2 arms mounted (big and small arm).

We are considering - if time and resources allow - to further try to create a Gazebo simulation of the Gateway. I am opening this Issue just to check in case somebody within the space-ros community is already doing something similar, as to avoid repeating efforts.

Our repo is here: https://github.com/traclabs/gateway_demos and an image of the Gateway in Rviz is attached:

Implementation considerations

Adding xacro/launch/config files.