update changelog

Author: RobinMalfait

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Discard matched variants with non-string values ([#18799](https://github.com/tailwindlabs/tailwindcss/pull/18799))
 - Show suggestions for known `matchVariant` values ([#18798](https://github.com/tailwindlabs/tailwindcss/pull/18798))
 - Migrate `aria` theme keys to `@custom-variant` ([#18815](https://github.com/tailwindlabs/tailwindcss/pull/18815))
+- Migrate `data` theme keys to `@custom-variant` ([#18816](https://github.com/tailwindlabs/tailwindcss/pull/18816))
 
 ## [4.1.12] - 2025-08-13