function onOpen() {
  let ui = SpreadsheetApp.getUi();
  ui.createMenu('Timesheets')
      .addItem('Form setup', 'setUpForm')
      .addItem('Column setup', 'columnSetup')
      .addItem('Notify employees', 'checkApprovedStatusToNotify')
      .addToUi();
}
Creates the menu item "Timesheets" for user to run scripts on drop-down.