Added changelog

Author: jonathanhertz

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -15,6 +15,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Added `NetworkTimeSystem.TickLatency` property that provides the average latency of a client. (#3337)
 - Added `FastBufferReader(ArraySegment<byte> buffer, Allocator copyAllocator)` constructor that uses the `ArraySegment.Offset` as the `FastBufferReader` offset and the `ArraySegment.Count` as the `FastBufferReader` length. (#3321)
 - Added `FastBufferReader(ArraySegment<byte> buffer, Allocator copyAllocator, int length = -1)` constructor that uses the `ArraySegment.Offset` as the `FastBufferReader` offset. (#3321)
+- Added `NetworkManager.OnPreShutdown` which is called before the NetworkManager cleans up and shuts down. (#3366)
 
 ### Fixed