support dark mode

[asterix314]

Proposal

As ver 0.19.0, great tables dos not display so great in dark mode. E.g., when I switch to dark mode in my marimo notebook, a typical great-tables table looks like this:

Only the table body background is changed to dark, making the text unreadable. The title, headers, footers, and stub area all remain light-colored. This proposal is asking for an automatic theme for dark mode due to its popularity.