增加Mediat Pip特性，并用实例来做一个demo

Core/MAX.Framework/DependencyInjection/ServiceCollectionExtensions.cs

@@ -64,6 +64,7 @@ namespace MAX.Framework.DependencyInjection
 			RunDebugStep("Plugin", "注册全部插件", () => RunPlugins(host, assemblies, instances));
 
 			RunDebugStep("Startup", "初始化并注册启动服务", () => RunStartups(host.Services, assemblies, instances));
+            RunDebugStep("MediatR", "按命令特性注册管道", () => host.Services.AddMediatRAttributedBehaviors(assemblies.ToArray()));