LibWeb: Implement IDBFactory::cmp

Author: https://github.com/stelar7
Commit: 331f26a88b
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2279
Reviewed-by: https://github.com/gmta
Reviewed-by: https://github.com/tcl3

Libraries/LibWeb/IndexedDB/IDBFactory.h

@@ -21,6 +21,7 @@ public:
     virtual ~IDBFactory() override;
 
     WebIDL::ExceptionOr<GC::Ref<IDBOpenDBRequest>> open(String const& name, Optional<u64> version);
+    WebIDL::ExceptionOr<i8> cmp(JS::Value first, JS::Value second);
 
 protected:
     explicit IDBFactory(JS::Realm&);