index.css

@import 'normalize.css';

index.js

require('./index.css')

package.json

{
  "name": "@data/css",
  "version": "0.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "browserify -p [./plugin.js -o bundle.css] -o bundle.js index.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "browserify": "^12.0.1",
    "css-modulesify": "^0.16.1",
    "normalize.css": "^3.0.3",
    "postcss-import": "^8.0.2",
    "postcss-reporter": "^1.3.1"
  }
}

plugin.js

// Browserify plugin
module.exports = function (browserify, options) {
  return browserify.plugin(require('css-modulesify'), Object.assign({
    after: [require('postcss-import'), require('postcss-reporter')]
  }, options))
}