Included the default serviceworker, updated the manifest, Add the default offline page, updated the unit test, Redme

pwa/templates/serviceworker.js

@@ -1,2 +1,53 @@
-// Empty Service Worker implementation.  To use your own Service Worker, set the PWA_SERVICE_WORKER_PATH variable in
-// settings.py
+// Base Service Worker implementation.  To use your own Service Worker, set the PWA_SERVICE_WORKER_PATH variable in settings.py
+
+var staticCacheName = "django-pwa-v" + new Date().getTime();
+var filesToCache = [
+    '/offline',
+    '/static/css/django-pwa-app.css',
+    '/static/images/icons/icon-72x72.png',
+    '/static/images/icons/icon-96x96.png',
+    '/static/images/icons/icon-128x128.png',
+    '/static/images/icons/icon-144x144.png',
+    '/static/images/icons/icon-152x152.png',
+    '/static/images/icons/icon-192x192.png',
+    '/static/images/icons/icon-384x384.png',
+    '/static/images/icons/icon-512x512.png',
+];
+
+// Cache on install
+self.addEventListener("install", event => {
+    this.skipWaiting();
+    event.waitUntil(
+        caches.open(staticCacheName)
+            .then(cache => {
+                return cache.addAll(filesToCache);
+            })
+    )
+});
+
+// Clear cache on activate
+self.addEventListener('activate', event => {
+    event.waitUntil(
+        caches.keys().then(cacheNames => {
+            return Promise.all(
+                cacheNames
+                    .filter(cacheName => (cacheName.startsWith("django-pwa-")))
+                    .filter(cacheName => (cacheName !== staticCacheName))
+                    .map(cacheName => caches.delete(cacheName))
+            );
+        })
+    );
+});
+
+// Serve from Cache
+self.addEventListener("fetch", event => {
+    event.respondWith(
+        caches.match(event.request)
+            .then(response => {
+                return response || fetch(event.request);
+            })
+            .catch(() => {
+                return caches.match('offline');
+            })
+    )
+});