update changelog

Author: RobinMalfait

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Don't mutate custom color palette when overriding per-plugin colors ([#6546](https://github.com/tailwindlabs/tailwindcss/pull/6546))
+- Improve circular dependency detection when using `@apply` ([#6588](https://github.com/tailwindlabs/tailwindcss/pull/6588))
 
 ## [3.0.6] - 2021-12-16