PWA Support

[grady-lad]

The current PWA features provided via create-react-app are currently disabled.

We should probably re-enable this feature so that our users don't have to re-download the js bundle when there are no new updates on the site.

It may also be worth our while to make the APP is to a fully functional PWA, allowing users to use to app just like a native mobile app, even with offline support ?

[grady-lad]

For now it would be nice to opt back in to using the service work to cache the bundle so users don't have to download the websites bundle every time they use the site.

Create react app provides this by default, we just need to re-enable this feature.