https://www.w3.org/TR/service-workers/
https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API
https://ponyfoo.com/articles/progressive-networking-serviceworker
https://gist.github.com/adactio/4d588bb8a65fa11a3ea3
https://brandonrozek.com/2015/11/limiting-cache-service-workers-revisited3/