Support specifying Three.js Tone Mapping for Meshcat

[nepfaff]

Is your feature request related to a problem? Please describe.
I want to share Meshcat HTMLs on project webpages so that people can play with Drake simulations. It would be nice if these would look a bit nicer.

Describe the solution you'd like
I want to be able to specify a Three.js Tone Mapping (e.g. AgX) through Meshcat. This would require a Meshcat JS code change here and associated Drake APIs.

Additional context
An example Meshcat that I think tone mapping would improve is the following:

[sherm1]

Assigned to Sean for disposition