LibWeb: Implement TransformStreamDefaultController::enqueue()

Author: https://github.com/kennethmyhra
Commit: 4ae82983a4
Pull-request: https://github.com/SerenityOS/serenity/pull/19998
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/shannonbooth

Userland/Libraries/LibWeb/Streams/TransformStreamDefaultController.h

@@ -19,6 +19,7 @@ public:
     virtual ~TransformStreamDefaultController() override;
 
     Optional<double> desired_size();
+    WebIDL::ExceptionOr<void> enqueue(Optional<JS::Value> chunk);
     WebIDL::ExceptionOr<void> error(Optional<JS::Value> reason = {});
 
     auto& flush_algorithm() { return m_flush_algorithm; }