LibWeb/IDB: Implement abort and wait steps for closing a connection

Author: https://github.com/stelar7
Commit: b6b00acbd1
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4306
Reviewed-by: https://github.com/ADKaster ✅

Libraries/LibWeb/IndexedDB/IDBTransaction.h

@@ -56,6 +56,7 @@ public:
     [[nodiscard]] bool is_upgrade_transaction() const { return m_mode == Bindings::IDBTransactionMode::Versionchange; }
     [[nodiscard]] bool is_readonly() const { return m_mode == Bindings::IDBTransactionMode::Readonly; }
     [[nodiscard]] bool is_readwrite() const { return m_mode == Bindings::IDBTransactionMode::Readwrite; }
+    [[nodiscard]] bool is_finished() const { return m_state == TransactionState::Finished; }
 
     WebIDL::ExceptionOr<void> abort();