LibWeb: Evaluate @media rules

We now evaluate the conditions of `@media` rules at the same point in
the HTML event loop as evaluation of `MediaQueryList`s. This is not
strictly to spec, but since the spec doesn't actually say when to do
this, it seems to make the most sense. In any case, it works! :^)

Userland/Libraries/LibWeb/CSS/CSSStyleSheet.cpp

@@ -67,4 +67,9 @@ bool CSSStyleSheet::for_first_not_loaded_import_rule(Function<void(CSSImportRule
     return m_rules->for_first_not_loaded_import_rule(callback);
 }
 
+void CSSStyleSheet::evaluate_media_queries(DOM::Window const& window)
+{
+    m_rules->evaluate_media_queries(window);
+}
+
 }