function columnSetup() {
  let sheet = SpreadsheetApp.getActiveSheet();
  let lastCol = sheet.getLastColumn();
  let lastRow = sheet.getLastRow();
  let frozenRows = sheet.getFrozenRows();
  let beginningRow = frozenRows + 1;
  let numRows = lastRow - frozenRows;

  // Calls helper functions to add new columns.
  addCalculatePayColumn(sheet, beginningRow);
  addApprovalColumn(sheet, beginningRow, numRows);
  addNotifiedColumn(sheet, beginningRow, numRows);
}
Adds "WEEKLY PAY" column with calculated values using array formulas. 
Adds an "APPROVAL" column at the end of the sheet, containing 
drop-down menus to either approve/disapprove employee timesheets.  
Adds a "NOTIFIED STATUS" column indicating whether or not an
employee has yet been e mailed.