Web Push Notifications


 * Google Developers:
 * Service Worker API: https://developers.google.com/web/fundamentals/getting-started/primers/service-workers
 * Web Push Notifications:
 * Overview - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/
 * What Makes a Good Notification? - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/good-notification
 * Requesting Permission and Subscribing Users - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/permissions-subscriptions
 * Sending Messages - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/sending-messages
 * Handling Messages - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/handling-messages
 * Video: Web Push Notifications (I/O 2016) - https://developers.google.com/web/fundamentals/engage-and-retain/push-notifications/video
 * Mozilla Developer network:
 * Push API: https://developer.mozilla.org/en-US/docs/Web/API/Push_API
 * Notification API: https://developer.mozilla.org/en-US/docs/Web/API/Notifications_API
 * Notification: https://developer.mozilla.org/en-US/docs/Web/API/notification