Added build script

src/sw.js

@@ -0,0 +1,26 @@
+var cacheName = 'telesec_%%VERSIONCO%%';
+
+self.addEventListener('install', event => {
+  event.waitUntil(
+    caches.open(cacheName)
+      .then(cache => cache.addAll(%%ASSETSJSON%%))
+  );
+});
+
+self.addEventListener('message', function (event) {
+  if (event.data.action === 'skipWaiting') {
+    self.skipWaiting();
+  }
+});
+
+self.addEventListener('fetch', function (event) {
+  event.respondWith(
+    caches.match(event.request)
+      .then(function (response) {
+        if (response) {
+          return response;
+        }
+        return fetch(event.request);
+      })
+  );
+});