- https://codelabs.developers.google.com/codelabs/your-first-pwapp-ja/index.html?index=..%2F..%2Findex#0
- http://www.html5rocks.com/en/tutorials/service-worker/introduction/
- https://jakearchibald.com/2014/offline-cookbook/
- http://tech.plaid.co.jp/cong-lai-nowebapurinochang-shi-wobian-eru-service-workergamotarasuwebnowei-lai/
- https://jakearchibald.com/2014/offline-cookbook/
using Network falling back to cache pattern.
ref: https://jakearchibald.com/2014/offline-cookbook/#network-falling-back-to-cache
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