fix SelectableHtml not rebuild when data change (#1111)

Co-authored-by: Do Cao Huynh <[email protected]>

Author: docaohuynh

lib/flutter_html.dart

@@ -335,7 +335,7 @@ class SelectableHtml extends StatefulWidget {
 }
 
 class _SelectableHtmlState extends State<SelectableHtml> {
-  late final dom.Element documentElement;
+  late dom.Element documentElement;
 
   @override
   void initState() {
@@ -344,6 +344,16 @@ class _SelectableHtmlState extends State<SelectableHtml> {
         ? HtmlParser.parseHTML(widget.data!)
         : widget.documentElement!;
   }
+  @override
+  void didUpdateWidget(SelectableHtml oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if ((widget.data != null && oldWidget.data != widget.data) ||
+        oldWidget.documentElement != widget.documentElement) {
+      documentElement = widget.data != null
+          ? HtmlParser.parseHTML(widget.data!)
+          : widget.documentElement!;
+    }
+  }
 
   @override
   Widget build(BuildContext context) {