Make use of service worker

[k1sul1]

Requests to local assets are automatically cached for offline support. Instead of logging things to console, these things could be made useful. Might also want to allow opt-out.

https://github.com/k1sul1/wp-plugin.pro/blob/master/src/registerServiceWorker.js#L59
https://github.com/k1sul1/wp-plugin.pro/blob/master/src/registerServiceWorker.js#L64
https://github.com/k1sul1/wp-plugin.pro/blob/master/src/registerServiceWorker.js#L97