code: function getDefaultVersion(filename) {
      const info = getPackageJson(filename)
      const nodeVersion = info && info.engines && info.engines.node
  
      return semver.validRange(nodeVersion) || DEFAULT_VERSION
  }
docs: Gets default version configuration of this rule.
  
  This finds and reads 'package.json' file, then parses 'engines.node' field.
  If it's nothing, this returns null.
  
  @param {string} filename - The file name of the current linting file.
  @returns {string} The default version configuration.