Dark Mode Support

[gbowlin]

Is your feature request related to a problem?

Not a problem, but it would be nice to support Dark Mode.

Describe the solution you'd like

General Dark Mode theme support.

Currently matplotlib backgrounds default to white. This can be fixed by adding , transparent=True to seismometer.plot.mpl._util's to_svg helper when calling plt.savefig

This is almost all that's needed.

Otherwise we would need:

• [ ] vscode theme support, plots by themselves support dark mode, but the Explore controls (and anything ipywidgets based) gets a white background still .
• [ ] plot updates, several legends would need to be updated to support a neutral background that can work in both light and dark modes.
• [ ] the altair plot for fairness audits would also need to support a more neutral background.

Describe alternatives you've considered

It might be possible to use the NotebookHost class from seismometer.core.nbhost to ask if the theme is light or dark, by inspecting the running environment. This doesn't handle dynamic theme changes very well, and would need special handling for each Host.

Additional context

What this looks like in vscode

What this looks like in jupyter lab