"parallel" options to leverage multiple cores [feature request]

[damianobarbati]

Dealing with webpack@4 migration and investigating uglify-es I noted the following: https://github.com/webpack-contrib/uglifyjs-webpack-plugin#parallel

Would this feature be possible too here?
I'm not sure whether it really means any improvement when minifying a "unique" big bundle or if it's just intended as parallel minifying of "smaller independent bundles/chunks".