function addNotifiedColumn(sheet, beginningRow, numRows) {
  sheet.insertColumnAfter(COLUMN_NUMBER.APPROVAL); // global
  sheet.getRange(1, COLUMN_NUMBER.APPROVAL + 1).setValue('NOTIFIED STATUS');

  // Make sure notified column is all drop-down menus.
  let notifiedColumnRange = sheet.getRange(beginningRow, COLUMN_NUMBER.APPROVAL
      + 1, numRows, 1);
  dropdownValues = ['NOTIFIED', 'PENDING'];
  rule = SpreadsheetApp.newDataValidation().requireValueInList(dropdownValues)
      .build();
  notifiedColumnRange.setDataValidation(rule);
  notifiedColumnRange.setValue('PENDING');  
}
Adds a NOTIFIED column allowing managers to see which employees
have/have not yet been notified of their approval status.

@param {Object} sheet Spreadsheet object of current sheet.
@param {Integer} beginningRow Index of beginning row.
@param {Integer} numRows Number of rows currently in use.