code: function getUnresolvedIconPath (value) {
    const relativePathResult = urlRegexp.exec(value);
    if (!relativePathResult) {
      throw new Error(`Could not parse url "${value}".`);
    }
    return relativePathResult[2] || relativePathResult[3] || relativePathResult[4];
  }
docs: Turn `url("demo.svg")` into `demo.svg`