Updated Service Worker JS and Added Node Server

Updated the service worker JS. Issue with how I typed the cache links. Forgot to put a "./" before the asset name. Should work now.

server.js

@@ -0,0 +1,26 @@
+/*
+Copyright 2018 Google Inc.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+   http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+const express = require('express');
+const app = express();
+
+// This serves static files from the specified directory
+app.use(express.static(__dirname));
+
+const server = app.listen(8081, () => {
+
+  const host = server.address().address;
+  const port = server.address().port;
+
+  console.log('App listening at http://%s:%s', host, port);
+});