chore(README.md): Add note about current stable version

Author: konradasb

README.md

@@ -4,6 +4,9 @@
 
 Fireactions is an orchestrator for GitHub runners. BYOM (Bring Your Own Metal) and run self-hosted GitHub runners in ephemeral, fast and secure [Firecracker](https://firecracker-microvm.github.io/) based virtual machines.
 
+> [!IMPORTANT]
+> There's been multiple improvements with a lot of breaking changes. The current stable version is **v2.0.0**. Please use this version for production environments.
+
 <!--
 https://excalidraw.com/#json=GrJMj6LLYt39mgC0me7Di,C65TV9FhicnxNKgPeRhi3A
 sequenceDiagram