LibWeb: Add calls to JS_{DECLARE,DEFINE}_ALLOCATOR()

Author: https://github.com/mattco98
Commit: 31341b280a
Pull-request: https://github.com/SerenityOS/serenity/pull/23878
Issue: https://github.com/SerenityOS/serenity/issues/23805
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibWeb/CSS/AnimationEvent.cpp

@@ -9,6 +9,8 @@
 
 namespace Web::CSS {
 
+JS_DEFINE_ALLOCATOR(AnimationEvent);
+
 JS::NonnullGCPtr<AnimationEvent> AnimationEvent::create(JS::Realm& realm, FlyString const& type, AnimationEventInit const& event_init)
 {
     return realm.heap().allocate<AnimationEvent>(realm, realm, type, event_init);