relativeCell(rowOffset, columnOffset) {
        const row = rowOffset + this.rowNumber();
        const column = columnOffset + this.columnNumber();
        return this.sheet().cell(row, column);
    }
Returns a cell with a relative position given the offsets provided.
@param {number} rowOffset - The row offset (0 for the current row).
@param {number} columnOffset - The column offset (0 for the current column).
@returns {Cell} The relative cell.