Update changelog with tuple struct serialization

Author: sigmaris

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+
+### Added
+
+- Support for serializing tuple structs. These are serialized as JSON arrays,
+  which matches `serde_json` behaviour.
+
 ## [v0.5.0] - 2022-11-04
 
 ### Changed
@@ -61,6 +68,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 Initial release
 
+[Unreleased]: https://github.com/rust-embedded-community/serde-json-core/compare/v0.5.0...HEAD
 [v0.5.0]: https://github.com/rust-embedded-community/serde-json-core/compare/v0.4.0...v0.5.0
 [v0.4.0]: https://github.com/rust-embedded-community/serde-json-core/compare/v0.3.0...v0.4.0
 [v0.3.0]: https://github.com/rust-embedded-community/serde-json-core/compare/v0.2.0...v0.3.0