Update changelog

Author: adamwathan

CHANGELOG.md

@@ -9,6 +9,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Nothing yet!
 
+## [2.0.0-alpha.4] - 2020-10-29
+
+### Added
+
+- Support deep merging of arrays of objects under `extend` ([#2700](https://github.com/tailwindlabs/tailwindcss/pull/2700))
+
 ## [2.0.0-alpha.3] - 2020-10-27
 
 ### Added
@@ -1070,7 +1076,8 @@ No release notes
 
 - Everything!
 
-[unreleased]: https://github.com/tailwindlabs/tailwindcss/compare/v2.0.0-alpha.3...HEAD
+[unreleased]: https://github.com/tailwindlabs/tailwindcss/compare/v2.0.0-alpha.4...HEAD
+[2.0.0-alpha.4]: https://github.com/tailwindlabs/tailwindcss/compare/v2.0.0-alpha.3...v2.0.0-alpha.4
 [2.0.0-alpha.3]: https://github.com/tailwindlabs/tailwindcss/compare/v2.0.0-alpha.2...v2.0.0-alpha.3
 [2.0.0-alpha.2]: https://github.com/tailwindlabs/tailwindcss/compare/v2.0.0-alpha.1...v2.0.0-alpha.2
 [1.9.6]: https://github.com/tailwindlabs/tailwindcss/compare/v1.9.5...v1.9.6