Added saving of token to web worker + Play with dark theme

public/js/workers/auth_worker.js

@@ -0,0 +1,16 @@
+self.onmessage = function (event) {
+  console.log(event.data);
+  const action = event.data.action;
+  switch(action) {
+    case 'save':
+      token = event.data.token;
+      break;
+    case 'load':
+      console.log(token);
+      break;
+    default:
+      console.error('Invalid action');
+      return;
+  }
+  self.postMessage(true);
+}