Add Directory.Build.props. (#2120)

* Add Directory.Build.props.

* Adjust Analysis related properties and add conditional enablement for ContinuousIntegrationBuild.

* Adopt new changes in master

---------

Co-authored-by: christian <6939810+chkr1011@users.noreply.github.com>

Source/MQTTnet.AspnetCore/SocketReceiver.cs

@@ -8,7 +8,7 @@ using System.Net.Sockets;
 
 namespace MQTTnet.AspNetCore;
 
-public sealed class SocketReceiver
+public sealed class SocketReceiver : IDisposable
 {
     readonly SocketAwaitable _awaitable;
     readonly SocketAsyncEventArgs _eventArgs = new();
@@ -33,4 +33,9 @@ public sealed class SocketReceiver
 
         return _awaitable;
     }
+
+    public void Dispose()
+    {
+        _eventArgs.Dispose();
+    }
 }