Manage xacro file from github

# Feature Request

As a recently new user of your solution, I want to visualise some robot thanks to their xacro so that I can edit xacro without ROS directly opened.

## Details

**Is your feature request related to a problem? Please describe.**
I need to launch ROS in order to update my xacro file that I currently visualise after conversion into Rhino.

**Describe the solution you'd like**
Two solution exist:
- execute the xacro.py converter from ROS and download the urdf resulting
- adapt it into compas_fab directly

**Describe alternatives you've considered**
I will use compas_fab in a ROS environment to be able to convert my xacro for now. But it would be great to visualise some xacro among the ros-industrial ones quickly.

Thank you very much for your great job