Dark UI theme for inline editors

This is a spinoff of @larz0's work in #8362 with a goal of fixing #8379.

As of this initial push, I have done inline CSS and color editors. The timing editor is almost done, and quick docs remains.

cc @MiguelCastillo
@larz0 In light theme, the selected state of *text* is now light blue, but I was expecting the *background* to be blue similar to dark theme. Is that intended?