code: async function workaroundEmptyStyleChunk (stats, outDir) {
    const styleChunk = stats.children[0].assets.find(a => {
      return /styles\.\w{8}\.js$/.test(a.name)
    })
    if (!styleChunk) return
    const styleChunkPath = path.resolve(outDir, styleChunk.name)
    const styleChunkContent = await fs.readFile(styleChunkPath, 'utf-8')
    await fs.remove(styleChunkPath)
    // prepend it to app.js.
    // this is necessary for the webpack runtime to work properly.
    const appChunk = stats.children[0].assets.find(a => {
      return /app\.\w{8}\.js$/.test(a.name)
    })
    const appChunkPath = path.resolve(outDir, appChunk.name)
    const appChunkContent = await fs.readFile(appChunkPath, 'utf-8')
    await fs.writeFile(appChunkPath, styleChunkContent + appChunkContent)
  }
docs: find and remove empty style chunk caused by
  https://github.com/webpack-contrib/mini-css-extract-plugin/issues/85
  TODO remove when it's fixed
  
  @param {Object} stats
  @param {String} outDir
  @returns {Promise<void>}