Add support for PWA.

[Alexintosh]

• Icon not working

• Add splash screen

• Clear PWA cache on app version change

[perminder-klair]

@Alexintosh we have issue with PWA service worker.
It updated cache whenever new code is pushed. But client/user can only use new code when closing and opening tab.
It does not works with refresh or hard refresh such as window.location.reload(true);

Solution, can be letting User know some kind of message like: "New update is available, please close this tab and open new one again."

Any suggestions?

[perminder-klair]

Or there is way by ejecting from CRA as discussed here: facebook/create-react-app#5316 (comment)

[perminder-klair]

opening again, as its not updating client production app after update.

[perminder-klair]

disabled PWA for now.