Update docs

Build/MQTTnet.nuspec

@@ -13,6 +13,7 @@
     <releaseNotes> * [Core] Performance optimizations.
 * [Core] Due to performance reasons the timestamp of log messages is now in UTC format.
 * [Client] Received messages are now processed in the worker thread by default. Added a new setting for switching back to dedicated threads.
+* [ManagedClient] Fixed a loading issue of stored application messages (thanks to @JTrotta).
 * [Server] Added support for other WebSocket sub protocol formats like mqttv-3.1.1 (thanks to @israellot).
 * [Server] The takeover of an existing client sessions is now treated as a _clean_ disconnect of the previous client.
 * [Server] The pending messages queue per client is now limited to 250 messages. Overflow strategy and count can be changed via options (thanks to @VladimirAkopyan)