Add AspNetCoreSseServer sample (#81)

* Add AspNetCoreSseMcpTransport sample

* Fix build errors after rebase

* React to McpServerFactory changes

* Make Utf8JsonWriter non thread static

* Fix test errors caused by not rebasing the HttpLister changes on factory overhaul commit

samples/AspNetCoreSseServer/Program.cs

@@ -0,0 +1,11 @@
+using McpDotNet;
+using AspNetCoreSseServer;
+
+var builder = WebApplication.CreateBuilder(args);
+builder.Services.AddMcpServer().WithTools();
+var app = builder.Build();
+
+app.MapGet("/", () => "Hello World!");
+app.MapMcpSse();
+
+app.Run();