Service Worker for PWA

[keithrfung]

Feature Request

Is your feature request related to a problem? Please describe.
Ideally this application should function additionally as a PWA so that it can be installed since all the services are run locally. Setting up a proper worker is the first step to this.

Describe the solution you'd like
Expand on existing worker.js to enable all functions as PWA. Convert the worker to Typescript with accompanying typescript definition