LibWeb: Create XMLDocuments in DOMImplementation.createDocument

Author: https://github.com/shannonbooth
Commit: cd156bad6b
Pull-request: https://github.com/SerenityOS/serenity/pull/22567
Reviewed-by: https://github.com/awesomekling

Tests/LibWeb/Text/input/DOM/DOMImplementation-create-xml-document.html

@@ -0,0 +1,7 @@
+<script src="../include.js"></script>
+<script>
+    test(() => {
+        const xmlDoc = document.implementation.createDocument(null, "books");
+        println(xmlDoc.constructor.name);
+    });
+</script>