update url-dispatch examples

examples/url-dispatch/src/resource.rs

@@ -0,0 +1,16 @@
+// <resource>
+use actix_web::{http::Method, App, HttpRequest, HttpResponse};
+
+fn index(req: HttpRequest) -> HttpResponse {
+    unimplemented!()
+}
+
+fn main() {
+    App::new()
+        .resource("/prefix", |r| r.f(index))
+        .resource("/user/{name}", |r| {
+            r.method(Method::GET).f(|req| HttpResponse::Ok())
+        })
+        .finish();
+}
+// </resource>