code: public static synchronized void cors() {
          checkStarted();
          instance().rootInterceptors.add(Interceptors.cors());
          instance().adminManager.addInterceptor(Interceptors.cors());
      }
docs: Enable CORS by setting:
  <ul>
  <li>Access-Control-Allow-Origin: *</li>
  <li>Access-Control-Allow-Credentials: true</li>
  <li>Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS, HEAD</li>
  <li>Access-Control-Allow-Headers: Origin, Accept, X-Requested-With, Content-Type, Authorization, Access-Control-Request-Method, Access-Control-Request-Headers</li>
  </ul>
  <p>
  For custom headers, use {@link SnappyServer#before(String, HttpConsumer)}