[sidecar] Include Plotly in bundle

[rgbkrk]

It's pretty common for people to use Plotly. Let's include it in our bundle and use the Plotly media type to render it directly in sidecar.

[rgbkrk]

Given plotly/plotly.py#4823, maybe there's an even simpler pathway. @manzt

[rgbkrk]

Plotly relies on anywidget now. I need to test it in sidecar but I'll call this done for now because I'm going to move the UI bits out of runtimed/runtimed into another repo.