copy(cell) {
        const newRichText = new RichText(_.cloneDeep(this.toXml()));
        if (cell && _.includes(this.text(), '\n')) {
            cell.style('wrapText', true);
        }
        return newRichText;
    }
Returns a deep copy of this instance.
If cell reference is provided, it checks line separators and calls
`cell.style('wrapText', true)` when needed.
@param {Cell|undefined} [cell] - The cell reference.
@return {RichText} A deep copied instance