Update CHANGELOG.md with unreleased version

Author: SamuelBellomo

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 Additional documentation and release notes are available at [Multiplayer Documentation](https://docs-multiplayer.unity3d.com).
 
+## [Unreleased]
+
+### Added
+### Fixed
+### Changed
+
 ## [1.14.0] - 2025-07-21
 
 ### Added