Feature request. Add an option to GZIP service-worker.js file.

The issue I'm experiencing is pretty annoying.
I'm trying to optimize my first byte, by turning off `compression`, and gziping everything by webpack with CompressionPlugin. The issue is that it doesn't compress `service-worker.js` produced by sw-precache-webpack-plugin.

I understand the reason why: `service-worker.js` should cache all chunks produced by webpack after CompressionPlugin compression.

This is why I think it should be an option in sw-precache-webpack-plugin itself.

Thank you)