Consistent theme for JSON pane and Code Editor

[MarcSkovMadsen]

(I plan to make a PR to fix this)

I'm on the main branch of Panel. I was developing a Panel Mermaid Diagram Editor using the JSON pane and CodeEditor widget and I experienced the friction that the theme of these two widget where not aligned and did not automatically adapt to pn.config.theme.

I believe the components should have a light theme if the overall theme is default. And a Black theme otherwise. I think the default themes should be user configurable.

Please support this

Minimum Reproducible Example

import panel as pn

pn.extension("codeeditor")

pn.template.FastListTemplate(
    main=[pn.widgets.CodeEditor(), pn.pane.JSON({"a": 1, "b": 2})]
).servable()

Default

Dark