code: function addBOMSignature (directory) {
      shell.ls('-R', directory)
          .map(function (file) {
              return path.join(directory, file);
          })
          .forEach(addBOMToFile);
  }
docs: Adds BOM signature at the beginning of all js|html|css|json files in
  specified folder and all subfolders. This is required for application to
  pass Windows store certification successfully.
  
  @param  {String}  directory  Directory where we need to update files