Add guide on URDF setup

[Ryan4253]

Describe the Task To ensure that future maintainers can quickly learn and set up robots, a guide on how to set up robot URDFs should be written

Goals: Guide should include the followig

• Explanation of URDF (can be a list of sources)
• Conventions
• Process of creating a URDF

Additional context Can potentially be done using Github Wiki, which allowed the guide to be directly attached to the stack

[Ryan4253]

Done, further edits / recommendations should be in a new issue