* `pc.color_mode`: a BaseVar that accesses colorMode on the frontend
* `pc.color_mode_cond`: a `pc.cond` wrapper that conditionally renders
components or props based on the value of `color_mode`
* `pc.color_mode_icon`: by default "sun" if light mode, "moon" if dark mode
* `pc.color_mode_switch`: a Switch component where is_checked depends on the
color_mode and changing the value calls toggle_color_mode
* `pc.color_mode_button`: a Button component that calls toggle_color_mode on click
The default template has been updated to include a color_mode_button with
color_mode_icon for toggling light/dark mode. The inline hover style has also
been updated to use color_mode_cond to show a different highlight color based
on the color_mode.
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