Easy way to disable plugin

[Arseniy-II]

Bug Report or Feature Request (mark with an x)

- [ ] bug report -> please search issues before submitting
- [X] feature request

Hello! Thanks for great pligin. It would be nice to have easy way to disable plugin

new ServiceWorkerWebpackPlugin({
    ...
    disable: proces.env.NODE_ENV !== 'production'
});

[Skagevang]

@oliviertassinari is this repo still maintained? This feature would be really nice to have