Update README.md (Azure#18489)

Add note that package is currently in Beta and is not yet fully supported.

Author: victoriachenm

sdk/resourcemanager/chaos/armchaos/README.md

@@ -3,6 +3,7 @@
 [![PkgGoDev](https://pkg.go.dev/badge/github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/chaos/armchaos)](https://pkg.go.dev/github.com/Azure/azure-sdk-for-go/sdk/resourcemanager/chaos/armchaos)
 
 The `armchaos` module provides operations for working with Azure Chaos.
+This package is currently in Beta and is not yet fully supported.
 
 [Source code](https://github.com/Azure/azure-sdk-for-go/tree/main/sdk/resourcemanager/chaos/armchaos)
 
@@ -74,4 +75,4 @@ This project has adopted the
 For more information, see the
 [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/)
 or contact [[email protected]](mailto:[email protected]) with any
-additional questions or comments.
+additional questions or comments.