Automatically set worker version

Have the generated `service-worker.js` (part of the `worker` package) automatically update the version. The version should change in dev mode and be set from the version in `package.json` in the production mode.

Start in the worker package and inspect how generated service-worker.js is produced, then compare the package.json version and the development and production paths. Done means the worker version changes in dev mode and uses package.json's version in production; verify both generation modes.

Written by the indexing model from the issue text.