move files for node only implementation

public/service-worker.js

@@ -0,0 +1,57 @@
+var CACHE_NAME = 'snapdrop-cache-v2';
+var urlsToCache = [
+  'index.html',
+  './',
+  'styles.css',
+  'scripts/network.js',
+  'scripts/ui.js',
+  'scripts/clipboard.js',
+  'scripts/theme.js',
+  'sounds/blop.mp3',
+  'images/favicon-96x96.png'
+];
+
+self.addEventListener('install', function(event) {
+  // Perform install steps
+  event.waitUntil(
+    caches.open(CACHE_NAME)
+      .then(function(cache) {
+        console.log('Opened cache');
+        return cache.addAll(urlsToCache);
+      })
+  );
+});
+
+
+self.addEventListener('fetch', function(event) {
+  event.respondWith(
+    caches.match(event.request)
+      .then(function(response) {
+        // Cache hit - return response
+        if (response) {
+          return response;
+        }
+        return fetch(event.request);
+      }
+    )
+  );
+});
+
+
+self.addEventListener('activate', function(event) {
+  console.log('Updating Service Worker...')
+  event.waitUntil(
+    caches.keys().then(function(cacheNames) {
+      return Promise.all(
+        cacheNames.filter(function(cacheName) {
+          // Return true if you want to remove this cache,
+          // but remember that caches are shared across
+          // the whole origin
+          return true
+        }).map(function(cacheName) {
+          return caches.delete(cacheName);
+        })
+      );
+    })
+  );
+});