Fix xacro for simulation compatibility

[gabrielcalmon]

Checklist

• I have performed a thorough review of my code
• [N/A] I have sufficiently commented my code
• [N/A ] The implementation follows the project style conventions
• [N/A] All project unit tests are passing
• [N/A] If relevant, documentation has been provided or updated to discuss the changes made
• [N/A] System integration tests were performed successfully

Changes Made

The alpha_bringup/launch/alpha.launch.py was crashing when using the simulation option.

As it can be found on the forum ROS Answers, the original format <mesh filename="package://alpha_description/meshes/[FILE].stl" /> to call the meshes is not suported by gazebo, just by RVIZ, so the simulation was not working properly. So, it was updated to <mesh filename="file://$(find alpha_description)/meshes/[FILE].stl" />, which support both RVIZ and Gazebo.

The file updeted were alpha_description/urdf/end_effectors/standard_jaws.urdf.xacro
and alpha_description/urdf/alpha.urdf.xacro

Also, it was found that the README.md instructions pointed for the wrong SSH path and owner of the repository.

Associated Issues

No associated Issues.

Testing

The alpha_bringup/launch/alpha.launch.py was tested both with use_sim=true and use_sim=false

[mergify]

Please target the main branch for development, we will backport the changes to humble for you if approved and if they don't break the API.