Add Test-MqttConnection and Show-MqttExamples cmdlets, update documentation

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

Source/MQTTnet.PowerShell/Cmdlets/TestMqttConnectionCmdlet.cs

@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Management.Automation;
+
+namespace MQTTnet.PowerShell.Cmdlets;
+
+[Cmdlet(VerbsDiagnostic.Test, "MqttConnection")]
+[OutputType(typeof(bool))]
+public class TestMqttConnectionCmdlet : PSCmdlet
+{
+    [Parameter(Mandatory = true, ValueFromPipeline = true)]
+    public required PsMqttSession Session { get; set; }
+
+    [Parameter]
+    public int TimeoutSeconds { get; set; } = 5;
+
+    protected override void ProcessRecord()
+    {
+        try
+        {
+            var client = Session.GetClient();
+            
+            if (!client.IsConnected)
+            {
+                WriteObject(false);
+                return;
+            }
+
+            var cts = new CancellationTokenSource(TimeSpan.FromSeconds(TimeoutSeconds));
+            client.PingAsync(cts.Token).GetAwaiter().GetResult();
+            
+            WriteObject(true);
+        }
+        catch
+        {
+            WriteObject(false);
+        }
+    }
+}