Update changelog

Author: thecrypticace

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet!
+### Added
+
+- _Experimental_: Add `@container-size` utility ([#18901](https://github.com/tailwindlabs/tailwindcss/pull/18901))
 
 ## [4.1.18] - 2025-12-11
 
@@ -30,10 +32,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Don’t emit color-mix fallback rules inside `@keyframes` ([#19419](https://github.com/tailwindlabs/tailwindcss/pull/19419))
 - CLI: Don't hang when output is `/dev/stdout` ([#19421](https://github.com/tailwindlabs/tailwindcss/pull/19421))
 
-### Added
-
-- _Experimental_: Add `@container-size` utility ([#18901](https://github.com/tailwindlabs/tailwindcss/pull/18901))
-
 ## [3.4.19] - 2025-12-10
 
 ### Fixed