code: function(relativePath, line) {
      const file = setupHelper.setupFolderAbsolutePath() + '/' + relativePath;
      return setupHelper.handleShellResponse(shell.exec('echo "' + line + '" >> ' + file));
    }
docs: Append line at the end of the file
  
  @param {string} relativePath - relative file path
  @param {string} line - line to be appended to file