Support contact results visualization in PlanarSceneGraphVisualizer

[RussTedrake]

This is one simple feature that we're missing in the jupyter (e.g. colab/binder) workflow. We have it for meldis (with ConnectContactResultsToDrakeVisualizer) and for meshcat.

[kamiradi]

Hi, I have modified the intial PlanarSceneGraphVisualizer to now display contact points and forces. As per our discussion here, I wanted to see if I could contribute this to the code base after getting your feedback.

[RussTedrake]

That sounds fantastic. Please do open a PR. I think @bernhardpg might be particular interested in seeing it land.

[bernhardpg]

Yes I'd be very excited to see this land. Happy to help out with the review! @RussTedrake @kamiradi

[kamiradi]

See #21074.