mergeCells method
Merge cells in the given range.
Implementation
Future<void> mergeCells(int row1, int col1, int row2, int col2) async {
await VolvoxGridService.MergeCells(MergeCellsRequest()
..gridId = _gridId
..range = (CellRange()
..row1 = row1
..col1 = col1
..row2 = row2
..col2 = col2));
notifyListeners();
}