[test] switch to service workers

dont merge to live until can be confirmed to work well

src/sw.js

@@ -0,0 +1,40 @@
+console.log('Hello from sw.js');
+
+if (workbox) {
+  console.log('Yay! Workbox is loaded 🎉');
+  workbox.routing.registerRoute(
+    new RegExp('https://fonts.(?:googleapis|gstatic).com/(.*)'),
+    workbox.strategies.cacheFirst({
+      cacheName: 'google-fonts',
+      plugins: [
+        new workbox.expiration.Plugin({
+          maxEntries: 30
+        }),
+        new workbox.cacheableResponse.Plugin({
+          statuses: [0, 200]
+        })
+      ]
+    })
+  );
+  workbox.routing.registerRoute(
+    /\.(?:png|gif|jpg|jpeg|svg)$/,
+    workbox.strategies.cacheFirst({
+      cacheName: 'images',
+      plugins: [
+        new workbox.expiration.Plugin({
+          maxEntries: 60,
+          maxAgeSeconds: 30 * 24 * 60 * 60 // 30 Days
+        })
+      ]
+    })
+  );
+  workbox.routing.registerRoute(
+    /\.(?:js|css)$/,
+    workbox.strategies.staleWhileRevalidate({
+      cacheName: 'static-resources'
+    })
+  );
+  workbox.googleAnalytics.initialize();
+} else {
+  console.log('Boo! Workbox didn\'t load 😬');
+}