Add example notebook for rigid body dynamics

[flferretti]

This PR adds an example notebook for showing the use of JaxSim as a multibody dynamics library. Moreover, some refinements to the existing examples have been made.

Closes #194

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📚 Documentation preview 📚: https://jaxsim--261.org.readthedocs.build//261/

[diegoferigo]

@flferretti I'm done with my updates to the notebook. Feel free to either review the changes or directly update it, if needed. In order to run successfully, it needs an unmerged change from the ongoing contact refactoring.

[flferretti]

Thanks a lot Diego! I have amended the last commit to remove the cell outputs, for the rest it looks great

[diegoferigo]

I am experience a broken rendering of video on the notebooks. Regardless, let me merge #265 first, then I'll rebase this PR on top of that one.

[flferretti]

I am experience a broken rendering of video on the notebooks. Regardless, let me merge #265 first, then I'll rebase this PR on top of that one.

If you look at the built docs in the PR description, the videos work fine. Do you have that problem only locally?

[diegoferigo]

I am experience a broken rendering of video on the notebooks. Regardless, let me merge #265 first, then I'll rebase this PR on top of that one.

If you look at the built docs in the PR description, the videos work fine. Do you have that problem only locally?

It was here, #265 (comment). My bad, I moved an import without also moving the export of MUJOCO_GL.