Update changelog

Author: adamwathan

CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add new `border-spacing` utilities ([#7102](https://github.com/tailwindlabs/tailwindcss/pull/7102))
 - Add `enabled` variant ([#7905](https://github.com/tailwindlabs/tailwindcss/pull/7905))
 - Add TypeScript types for the `tailwind.config.js` file ([#7891](https://github.com/tailwindlabs/tailwindcss/pull/7891))
+- Add `backdrop` variant ([#7924](https://github.com/tailwindlabs/tailwindcss/pull/7924))
 
 ## [3.0.23] - 2022-02-16