[Draft] Add new PowerShell module

[chkr1011]

This PR adds a new project which contains a PowerShell module so that MQTTnet can also be used in PowerShell.

[ArakniD]

consider RegisterMqttMessageHandlerCmdlet to include the following implementation

        EventHandler<PsMqttMessage> handler = (s, e) =>
        // Capture the ScriptBlock and current default runspace (available during cmdlet execution)
        var scriptBlock = Action ?? throw new ArgumentNullException(nameof(Action));
        var capturedRunspace = Runspace.DefaultRunspace ?? throw new InvalidOperationException("No default runspace available during cmdlet execution.");

        EventHandler<PsMqttMessage> handler = null!;
        handler = (sender, e) =>
        {
            //throw new NotImplementedException();
            //InvokeCommand.InvokeScript(Action, false, PipelineResultTypes.Output, null, new object[] { e.Topic, e.Payload });
            // Run asynchronously to avoid blocking the event thread
            Task.Run(() =>
            {
                // Temporarily set the default runspace for this thread
                var originalRunspace = Runspace.DefaultRunspace;
                Runspace.DefaultRunspace = capturedRunspace;
        
                try
                {
                    // Invoke the ScriptBlock directly with arguments (returns Collection<PSObject>)
                    var results = scriptBlock.Invoke(e.Topic, e.Payload, e); // Pass topic, payload, and full message
        
                    // Handle output manually (e.g., write to host/console)
                    foreach (var result in results)
                    {
                        Host.UI.WriteLine(result?.ToString() ?? string.Empty);
                    }
                }
                catch (Exception ex)
                {
                    // Handle errors by writing to host error stream
                    Host.UI.WriteErrorLine($"MQTT handler error: {ex.Message}");
                    // Optionally: Host.UI.WriteVerboseLine(ex.StackTrace); for more details
                }
                finally
                {
                    // Restore the original default runspace for this thread
                    Runspace.DefaultRunspace = originalRunspace;
                }
            });
        };

gives an example usage of

    Register-MqttMessageHandler -Session $session -Action {
           param($topic, $payload, $message)
            try {
                #Write-Host "Received MQTT message on $topic  $payload"
                Add-Content -Path $script:currentFile -Value $payload
            } catch {
                Unsubscribe-MqttTopic -Session $session -Topic $Topic
                Write-Host "Un-Subscripion due to error."
                
                Disconnect-MqttSession -Session $session
                Write-Host "Mqtt disconnec due to error."
            }
    # Or do processing: Send-MqttResponse -Topic $topic -Payload "Ack: $payload"
    }
Write-Host "Registered msg handler added."