Add CHANGELOG entry

Author: simon-lemay-unity

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -10,6 +10,8 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Added
 
+- It is now possible to control which port clients will bind to using the `UnityTransport.ConnectionData.ClientBindPort` field. If not set, clients will bind to an ephemeral port (same as before this change). (#3764)
+
 
 ### Changed