LibWeb+LibJS: Move some code around to make CSS/Parser parse faster

This makes it possible to include fewer full definitions of things,
which makes the file about 30% faster to compile.

Userland/Libraries/LibWeb/DOM/StaticNodeList.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <LibJS/Heap/Heap.h>
+#include <LibJS/Runtime/Error.h>
 #include <LibWeb/DOM/StaticNodeList.h>
 
 namespace Web::DOM {