Creating Gzip files while build

Created by: Ayc0

With the current config of CRA when you build the project, the files aren't gzipped so if you want to serve gzipped files, you have to either gzipped dynamically or to eject.

What could be awesome is when a build is run, two folders are created in the build folder: one regular and one with the gzipped files. Or having the possibility to set a env var GZIP and build only one folder, gzipped or not