Typescript serviceWorker.register() types fails out of the box because of required config parameter

Created by: eddedd88

Environment

Typescript

Steps to Reproduce

1. Start an app with typescript: create-react-app --typescript test-app
2. Enable PWA by following the steps here: https://facebook.github.io/create-react-app/docs/making-a-progressive-web-app
3. The method serviceWorker.register() works fine in js, but in typescript the config argument is mandatory which causes the build to fail.