code: function getEnginesNode(filename) {
      const info = getPackageJson(filename)
      return getSemverRange(info && info.engines && info.engines.node)
  }
docs: Get the `engines.node` field of package.json.
  @param {string} filename The path to the current linting file.
  @returns {Range|null} The range object of the `engines.node` field.