replaceSlotMarkdown(el, component) {
    if (!el) return;
    if (!component.slotMarkdown) return;
    component.slotMarkdown = this.convertMarkdown(component.slotMarkdown);
    component.slotMarkdown = this.sanitiseHTML(component.slotMarkdown);
    el.innerHTML = component.slotMarkdown;
  }
Replace or add an HTML element's slot from a Markdown string
Only does something if the markdownit library has been loaded to window.
Will use DOMPurify if that library has been loaded to window.
@param {Element} el Reference to the element that we want to update
@param {*} component The component we are trying to add/replace