Update docs/release-notes/v0.43.0.md

Co-authored-by: Reshma Abdul Rahim <[email protected]>
Signed-off-by: Nithya Subramanian <[email protected]>

docs/release-notes/v0.43.0.md

@@ -13,6 +13,8 @@ If you're new to Radius, check out our website, [radapp.io](https://radapp.io),
 ### DeploymentTemplate Controller
 A new Kubernetes controller in Radius called the DeploymentTemplate Controller is now available that will allow users to deploy resources defined in Bicep manifests using Kubernetes tooling using Radius. This controller was added to enable integrations with GitOps platforms like Flux, which will be available in a future release. Please see the [DeploymentTemplate Controller design document](https://github.com/radius-project/design-notes/blob/main/architecture/2024-10-deploymenttemplate-controller.md) for more details.
 
+## rad CLI command for creating new resource types
+We have added a CLI command `rad resource-type create` to create new resource-types in Radius. This was added to enable resource extensibility in Radius. The end-end functionality of creating and deploying a user-defined resource type will be available in a future release. Learn more from the [UDT technical design document](https://github.com/radius-project/design-notes/blob/main/architecture/2024-07-user-defined-types.md)
 ## Breaking changes
 
 None