LibWeb/IDB: Implement IDBIndex::open_cursor

Author: https://github.com/stelar7
Commit: 63e1cc7b50
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4650
Reviewed-by: https://github.com/AtkinsSJ ✅

Libraries/LibWeb/IndexedDB/IDBIndex.h

@@ -33,6 +33,8 @@ public:
     GC::Ref<IDBTransaction> transaction() { return m_object_store_handle->transaction(); }
     GC::Ref<Index> index() { return m_index; }
 
+    [[nodiscard]] WebIDL::ExceptionOr<GC::Ref<IDBRequest>> open_cursor(JS::Value, Bindings::IDBCursorDirection = Bindings::IDBCursorDirection::Next);
+
 protected:
     explicit IDBIndex(JS::Realm&, GC::Ref<Index>, GC::Ref<IDBObjectStore>);
     virtual void initialize(JS::Realm&) override;