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