Add working but unstyled notify registration modal

web/utils/browserPushNotifications.ts

@@ -0,0 +1,3 @@
+export default function isPushNotificationSupported() {
+  return 'serviceWorker' in navigator && 'PushManager' in window;
+}

web/utils/localStorage.ts

@@ -1,5 +1,6 @@
 export const LOCAL_STORAGE_KEYS = {
   username: 'username',
+  hasDisplayedNotificationModal: 'HAS_DISPLAYED_NOTIFICATION_MODAL',
 };
 
 export function getLocalStorage(key) {