hopefully last fix

Author: Ellerbach

nanoFramework.Azure.Devices.Client.nuspec

@@ -22,6 +22,7 @@ This is an SDK for Azure IoT Hub using MQTT broker.</description>
       <dependency id="nanoFramework.CoreLibrary" version="1.15.5" />
       <dependency id="nanoFramework.Json" version="2.2.160" />
       <dependency id="nanoFramework.M2Mqtt" version="5.1.158" />
+      <dependency id="nanoFramework.M2Mqtt.Core" version="5.1.158" />
       <dependency id="nanoFramework.System.Net.Http" version="1.5.99" />
     </dependencies>
   </metadata>