Use Browserslist config

[ai]

It will be nice to respect the user’s Browserslist config.

We can do it with code like:

let browserslist = require('browserslist')

const baseBrowsers = browserslist()
const es6 = browserslist('supports es6-module')

const modernBrowsers = baseBrowsers.filter(i => es6.includes(i))
const legacyBrowsers = baseBrowsers.filter(i => !es6.includes(i))

[DanielSchaffer]

Hey, this is pretty clever. I like it!

[ai]

I made PR to do this trick #87

With recent Browserslist 4.16, we can do it even more elegant by browserslist config query.