Show info for selected agent

[blairlyons]

• [x] https://github.com/simularium/simularium-planning/issues/141
• [x] https://github.com/simularium/simularium-website/issues/411

Use Case

As a user, I want to be able to see information about the current selected agent, so that I can more easily debug or explore the trajectory.

Acceptance Criteria

Users can see details about the selected agent in the UI.