@api
    modalFooter$$(selectors = '') {
        return selectAll(this.template, LIGHTNING_MODAL_FOOTER, selectors);
    }
Query select multiple elements in lightning-modal-footer
Usage:
- `elem.modalFooter$$()` Returns all nodes in footer
- `elem.modalFooter$$('button, [data-button]')` Returns buttons in footer
@param {string} selectors Ex: 'div', 'button, [data-button]'
@returns elements[]