Update README.md before archiving (#66)

Author: mosuem

README.md

@@ -1,3 +1,6 @@
+> [!IMPORTANT]  
+> This repo has moved to https://github.com/dart-lang/tools/tree/main/pkgs/browser_launcher
+
 [![Dart](https://github.com/dart-lang/browser_launcher/workflows/Dart/badge.svg)](https://github.com/dart-lang/browser_launcher/actions?query=workflow%3ADart+branch%3Amaster)
 [![pub package](https://img.shields.io/pub/v/browser_launcher.svg)](https://pub.dev/packages/browser_launcher)
 [![package publisher](https://img.shields.io/pub/publisher/browser_launcher.svg)](https://pub.dev/packages/browser_launcher/publisher)