Add deprecation note

Author: NoahStolk

README.md

@@ -1,5 +1,8 @@
 # Detach
 
+> ️⚠️ **NOTE:** This project has been superseded by a new game engine and will not receive new updates.
+> The new engine is currently not open source.
+
 A set of (opinionated) libraries for developing lightweight, cross-platform, real-time applications and games in .NET 9. The libraries are currently in development and experimental, so expect breaking changes.
 
 These projects are also mainly for personal use, so don't expect support for older versions of .NET.