update changelog for version 8.3.0 release

Author: Sephster

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+
+## [8.3.0] - released 2021-06-03
 ### Added
 - The server will now validate redirect uris according to rfc8252 (PR #1203)
 - Events emitted now include the refresh token and access token payloads (PR #1211)
@@ -539,7 +541,8 @@ Version 5 is a complete code rewrite.
 
 - First major release
 
-[Unreleased]: https://github.com/thephpleague/oauth2-server/compare/8.2.4...HEAD
+[Unreleased]: https://github.com/thephpleague/oauth2-server/compare/8.3.0...HEAD
+[8.3.0]: https://github.com/thephpleague/oauth2-server/compare/8.2.4...8.3.0
 [8.2.4]: https://github.com/thephpleague/oauth2-server/compare/8.2.3...8.2.4
 [8.2.3]: https://github.com/thephpleague/oauth2-server/compare/8.2.2...8.2.3
 [8.2.2]: https://github.com/thephpleague/oauth2-server/compare/8.2.1...8.2.2