message: import base CSS from the built file
diff: import React from 'react'
  import Document, {Head, Main, NextScript} from 'next/document'
  -import BaseCSS from '../css'
  +// this relies on the raw-loader rule in next.config.js's webpack()
  +import baseCSS from '../dist/primer-components.css'
  import {ServerStyleSheet} from 'styled-components'
  import {extractCritical} from 'emotion-server'
  @@ -30,8 +31,8 @@ export default class MyDocument extends Document {
  <meta charSet="utf8" />
  <link rel="icon" href={asset('/static/assets/favicon.png')} />
  <link rel="apple-touch-icon" href={asset('/static/assets/apple-touch-icon.png')} />
  - <BaseCSS />
  - <style data-emotion>{css}</style>
  + <style id="primer-components">{baseCSS}</style>
  + <style id="emotion-static">{css}</style>
  {styles}
  <meta name="viewport" content="width=device-width,initial-scale=1" />
  <meta name="og:title" content="Primer React" />
  