function bulkAppendRows_(sheet, rows) {
  let startRow = sheet.getLastRow() + 1;
  let startColumn = 1;
  let numRows = rows.length;
  let numColumns = rows[0].length;
  sheet.getRange(startRow, startColumn, numRows, numColumns).setValues(rows);
}
Faster version of appending multiple rows via ranges. Requires all rows are equal length.

@param {Sheet} sheet - Sheet to append to
@param {Array<Array<object>>} rows - Rows to append