Add MyEvent activity to Elsa services

This change integrates the MyEvent activity into the Elsa Workflow engine configuration. It ensures that the MyEvent activity is available for workflows in the console application. This setup is essential for utilizing custom events within the application's workflow definitions.

samples/console/Elsa.Samples.ConsoleApp.Bookmarks/Program.cs

@@ -9,7 +9,7 @@ using Microsoft.Extensions.DependencyInjection;
 var services = new ServiceCollection();
 
 // Add Elsa services.
-services.AddElsa();
+services.AddElsa().AddActivity<MyEvent>();
 
 // Build service container.
 var serviceProvider = services.BuildServiceProvider();