Add EnvelopeGenerator.WorkerService as background worker

Added a new WorkerService project to the solution, targeting .NET 8.0 and using Microsoft.Extensions.Hosting. Implemented a Worker class that logs periodically, set up hosting in Program.cs, and included configuration files for logging and development. Updated the solution file to include and configure the new project.

EnvelopeGenerator.WorkerService/Worker.cs

@@ -0,0 +1,24 @@
+namespace EnvelopeGenerator.WorkerService
+{
+    public class Worker : BackgroundService
+    {
+        private readonly ILogger<Worker> _logger;
+
+        public Worker(ILogger<Worker> logger)
+        {
+            _logger = logger;
+        }
+
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                if (_logger.IsEnabled(LogLevel.Information))
+                {
+                    _logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
+                }
+                await Task.Delay(1000, stoppingToken);
+            }
+        }
+    }
+}