When working in a codebase with a lot of styles, and a need to keep a

level of backwards-compatibility while transitioning to newer components

or selectors, it can be difficult to know when a part of the UI is using

something that's now deprecated.
To help work with this, Ink now provides some useful deprecation

utilities.
An .ink-deprecated CSS class can now mark an element as deprecated.

This is useful for components or templates that are expected to go away.
An #ink-ns-ui.deprecated() mixin marks whatever it's mixed into as

deprecated. This is useful for styles.
These won't do anything by themselves, but when an affected element

resides within an element containing an .ink-show-deprecations CSS

class, the element will gain a double-outline offset from the element

that cycles through a series of colors. This provides a visual that

works in light and dark modes that will help draw attention to the

element, without affecting layout.
Consumers of Ink are encouraged to make use of this.

Tested in Storybook and in Review Board, with and without the opt-in

ink-show-deprecations CSS class.