visitHyperlink method
Implementation
@override
String visitHyperlink(HyperlinkNode node) {
final content = node.content.isNotEmpty
? node.content.map((it) => visit(it)).join("")
: '<mtext>${_escapeXml(node.url)}</mtext>';
return '<mrow href="${_escapeXml(node.url)}">$content</mrow>';
}