LibWeb: Add support for the options variant of {add,remove}EventListener

This also adds a variant of {add,remove}_event_listener called
{add,remove}_event_listener_with_options.

This is used internally to perform {add,remove}_event_listener with a
default constructed options struct. It was done like this because
default constructing the Variant with the options struct requires the
struct defintions to be present, which requires us to include
AbortSignal.h, which would cause a circular include as AbortSignal.h
includes EventTarget.h.

Userland/Libraries/LibWeb/Forward.h

@@ -108,6 +108,8 @@ class Text;
 class Timer;
 class Window;
 enum class QuirksMode;
+struct EventListenerOptions;
+struct AddEventListenerOptions;
 
 template<typename ValueType>
 class ExceptionOr;