code: function styleTag (opts) {
    var hex = opts.hash.toString('hex').slice(0, 16)
    var link = `${opts.base || ''}/${hex}/bundle.css`
    return `<link rel="preload" as="style" href="${link}" onload="this.rel='stylesheet'">`
  }
docs: NOTE: in theory we should be able to add integrity checks to stylesheets too, but in practice it turns out that it conflicts with preloading. So it's best to disable it for now. See: https://twitter.com/yoshuawuyts/status/920794607314759681