Setup initial import of 'worker_threads' node library

Author: hegelocampus

lib/src/node/worker_threads.dart

@@ -0,0 +1,22 @@
+// Copyright 2017 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:js/js.dart';
+
+class WorkerOptions extends Object {
+}
+
+@JS("worker_threads")
+class Worker {
+  external Worker on(String message, Function callback);
+
+  external factory Worker(String filename, WorkerOptions options);
+}
+
+@JS("worker_threads")
+class ParentPort {
+  external ParentPort postMessage(Object value,
+      {List transferList = const []});
+}
+