src/block.js
src/editor.scss
src/style.scss

module.exports = {
  entry: 'block.js',
  output: ...,
  module: ...,
  plugins: [new MiniCssExtractPlugin()],
  ...
}

import 'editor.scss'
import 'style.scss'

dist/block.js -> es5
dist/editor.css
dist/style.css

dist/block.js
dist/block.css