FIX: Undo/redo delete/add page

Now we can undo adding or deleting worksheets

base/src/test/user_model/mod.rs

@@ -16,6 +16,7 @@ mod test_paste_csv;
 mod test_rename_sheet;
 mod test_row_column;
 mod test_sheet_state;
+mod test_sheets_undo_redo;
 mod test_styles;
 mod test_to_from_bytes;
 mod test_undo_redo;