Update changelog

Author: adamwathan

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `rgb` and `hsl` color helpers for CSS variables ([#7665](https://github.com/tailwindlabs/tailwindcss/pull/7665))
 - Support PostCSS `Document` nodes ([#7291](https://github.com/tailwindlabs/tailwindcss/pull/7291))
 - Add `text-start` and `text-end` utilities ([#6656](https://github.com/tailwindlabs/tailwindcss/pull/6656))
+- Support customizing class name when using `darkMode: 'class'` ([#5800](https://github.com/tailwindlabs/tailwindcss/pull/5800))
 
 ## [3.0.23] - 2022-02-16