Add cache-loader to speed up builds

Created by: Timer

There's a little speed boost for yarn build. ¯\_(ツ)_/¯

no `cache-loader`
real	1m4.240s
real	0m58.490s

`cache-loader`:
real	0m57.913s
real	0m48.341s

https://github.com/facebookincubator/create-react-app/issues/2037