Replaces hardcoded CSS colors with Codex design tokens
for the purposes of improving dark-mode support.
These changes resolves issues where text was
illegible in dark-mode (white text on white background).
Bug: T367362
Change-Id: I6314c8013839ac1e9a67178be7d1cb4bc45a3321
* Add hover and active styles to match normal toolbar state styling.
* Move border from right to left on `.section-secondary .group`.
* Add a skinStyle for MonoBook so it doesn't get the button style,
because it provides its own.
Bug: T303991
Change-Id: I6f08906156a9768729d779b6c50c9e804f51fb98
