Add CRA typescript template with web & service worker

[JohannesMerkt]

This is the first iteration on a template that not only uses webworkers to not block the main ui thread, but also makes use of a service worker to cache opencascade.js files for faster resumption when visiting the page again.

The template is based on the newest cra-template-pwa-typescript from create-react-app. So this template is very up to date compared to the Create-React-App templates.

Im not sure if this template should be combined with the webworker template. Since i am not sure if it is a good idea to have additional boilerplate code for developers that do not intent to use the service worker at all.

[paulftw]

I'm not sure if this PR is abandoned or not, but I'd suggest using comlink. It would make code simpler and easier to review.