https://medium.freecodecamp.org/progressive-web-apps-bridging-the-gap-between-web-and-mobile-apps-a08c76e3e768

https://medium.com/@kennethrohde/progressive-web-apps-coming-to-all-chrome-platforms-80e31272e2a8

https://codeburst.io/an-introduction-to-service-workers-in-javascript-27d6376460c2?source=placement_card_footer_grid———1-60