Add new properties and events for the managed client.

Source/MQTTnet.Extensions.ManagedClient/MqttManagedProcessFailedEventArgs.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace MQTTnet.Extensions.ManagedClient
+{
+    public class MqttManagedProcessFailedEventArgs : EventArgs
+    {
+        public MqttManagedProcessFailedEventArgs(Exception exception)
+        {
+            Exception = exception;
+        }
+
+        public Exception Exception { get; }
+    }
+}