The custom element. Imports a default and darkmode color
palette and provides a toggle to swap between them. To use the themes,
elements in the page should set colors via the variable provided in
Such as --primary, --on-primary, --background, --on-background, etc. Some
additional classes are provided for convenience (primary-container-theme-sk,
secondary-container-theme-sk, surface, etc)
To change the color themes override the css variables in a ':root' selector.