LibWeb: Bring up basic external script execution in the new parser

This only works in some narrow cases, but should be enough for our own
welcome.html at least. :^)

Libraries/LibWeb/DOM/Document.cpp

@@ -424,4 +424,9 @@ void Document::set_pending_parsing_blocking_script(Badge<HTMLScriptElement>, HTM
     m_pending_parsing_blocking_script = script;
 }
 
+NonnullRefPtr<HTMLScriptElement> Document::take_pending_parsing_blocking_script(Badge<HTMLDocumentParser>)
+{
+    return m_pending_parsing_blocking_script.release_nonnull();
+}
+
 }