Add a `url` and a `extraScript` parameter to `createNoopServiceWorkerMiddleware`

Created by: hesyifei

Sometimes an app's service worker might not be named /service-worker.js. It would be useful to allow developers to customize the url/filename for the no-op service worker. (Since url parameter will be default to '/service-worker.js', there will be no change in current app's behavior.)

Also, the developers may want to includes additional code (such as a importScripts) in the service worker during development. A extraScript parameter would be very helpful in this case.