Update README.md before archiving (#68)

Author: mosuem

README.md

@@ -1,3 +1,6 @@
+> [!IMPORTANT]  
+> This repo has moved to https://github.com/dart-lang/tools/tree/main/pkgs/test_reflective_loader
+
 [![Build Status](https://github.com/dart-lang/test_reflective_loader/workflows/Dart/badge.svg)](https://github.com/dart-lang/test_reflective_loader/actions)
 [![pub package](https://img.shields.io/pub/v/test_reflective_loader.svg)](https://pub.dev/packages/test_reflective_loader)