Update changelog

Author: adamwathan

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Support flattening deeply nested color objects ([#2148](https://github.com/tailwindlabs/tailwindcss/pull/2148))
+- Support defining presets as functions ([#2680](https://github.com/tailwindlabs/tailwindcss/pull/2680))
 
 ## [2.0.0-alpha.2] - 2020-10-25