Variable scope classes

Classes that re-declare the token CSS variables on an element (`variables`, `theme-*`, `sizing-*`).

These classes re-declare token variables on an element, for example to pin a subtree to one theme (theme-dark) or one breakpoint’s sizes (sizing-lg). The variables themselves are listed on the token reference pages.

Class	Styles
`variables`	Declares 1434 custom properties across 3 rules (themes and breakpoints).
`variables-themes`	Declares 873 custom properties across 3 rules (themes and breakpoints).
`variables-sizing`	Declares 432 custom properties.
`theme-default`	Declares 291 custom properties.
`theme-dark`	Declares 291 custom properties.
`sizing-sm`	Declares 432 custom properties.
`sizing-md`	Declares 432 custom properties.
`sizing-lg`	Declares 432 custom properties.