Make use of the [`color-scheme` meta tag][0] to style buttons and other
widgets to match the selected color scheme.
When the scheme is toggled, the `content` of the tag is set to "light"
or "dark" to tell the user agent how to theme input elements, which
should match the colors of the rest of the app.
[0]: https://html.spec.whatwg.org/multipage/semantics.html#meta-color-scheme
