feat: add pub/sub support to dispatcher

Notifications are broadcast to zero or more handlers with configurable
publishing strategies (sequential or parallel) and pipeline behavior
support.

src/request.dispatcher/NotificationInvoker.cs

@@ -39,7 +39,7 @@ internal sealed class NotificationInvoker<TNotification> : NotificationInvoker
 
 		static NotificationHandlerDelegate<TNotification> Chain(NotificationHandlerDelegate<TNotification> next, INotificationBehavior<TNotification> behavior)
 		{
-			return [StackTraceHidden] (n, ct) => behavior.HandleAsync(n, next, ct);
+			return [StackTraceHidden](n, ct) => behavior.HandleAsync(n, next, ct);
 		}
 
 		Task Terminal(TNotification n, CancellationToken ct)