Update release notes.

Build/MQTTnet.nuspec

@@ -12,6 +12,7 @@
     <requireLicenseAcceptance>true</requireLicenseAcceptance>
     <description>MQTTnet is a high performance .NET library for MQTT based communication. It provides a MQTT client and a MQTT server (broker) and supports v3.1.0, v3.1.1 and v5.0.0 of the MQTT protocol.</description>
     <releaseNotes>
+* [ManagedClient] Extended ReconnectAsync (thanks to @nvsnkv, #1202). 
 * [MQTTnet.Server] Moved server project to a dedicated GitHub repository.
 
 Git commit: $gitCommit