Add unit test to ensure compatibility with `urdfdom` XSD

[marip8]

Per this comment, we should add a unit test to ensure the customizations added to the tesseract URDF parser comply with the urdfdom XSD.

[marip8]

@rjoomen do you know if this is can be an automated process? Or would we need to parse the urdfdom XSD file and make sure we don't have conflicting elements?

[rjoomen]

Something like this?

• Have some Tesseract URDF files for testing in this repo that showcase all possible Tesseract URDF features.
• Clone the XSD from the urdfdom repo in the testing Github workflow.
• Create test cases validating the URDFs against the XSD using some C++ library that supports this. This introduces an extra dependency, but only for testing.