docs: add migration notice (#1544)

Author: simar7

README.md

@@ -1,8 +1,7 @@
 # defsec
 
-_defsec_ is a cloud security rules engine.
-
-Please see [CONTRIBUTING.md](CONTRIBUTING.md) and [ARCHITECTURE.md](ARCHITECTURE.md) for more information.
+## 📣 Integration into Trivy
+_defsec_ codebase has now been fully integrated into [Trivy](https://github.com/aquasecurity/trivy). Going forwards, please open new discussions and pull requests in the Trivy repo.
 
 _defsec_ is an [Aqua Security](https://aquasec.com) open source project.
 Learn about our open source work and portfolio [here](https://www.aquasec.com/products/open-source-projects/).