LibWeb/DOM: Add FIXMEs for missing functions in Node

Author: https://github.com/jamierocks
Commit: https://github.com/LadybirdBrowser/ladybird/commit/116c1f835df
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/682
Reviewed-by: https://github.com/tcl3 ✅

Userland/Libraries/LibWeb/DOM/Node.idl

@@ -54,6 +54,10 @@ interface Node : EventTarget {
     unsigned short compareDocumentPosition(Node? otherNode);
     boolean contains(Node? other);
 
+    [FIXME] DOMString? lookupPrefix(DOMString? namespace);
+    [FIXME] DOMString? lookupNamespaceURI(DOMString? prefix);
+    [FIXME] boolean isDefaultNamespace(DOMString? namespace);
+
     [ImplementedAs=pre_insert, CEReactions] Node insertBefore(Node node, Node? child);
     [CEReactions] Node appendChild(Node node);
     [CEReactions] Node replaceChild(Node node, Node child);