Added migration info to README.md (#1024)

* Added migration info to README.md

Signed-off-by: Sebastian Schuster <[email protected]>

* Added example command

Signed-off-by: Sebastian Schuster <[email protected]>

---------

Signed-off-by: Sebastian Schuster <[email protected]>

Author: sschu

README.md

@@ -4,6 +4,14 @@ Terraform provider for [Keycloak](https://www.keycloak.org/).
 > [!NOTE]
 > Please note that this is currently work-in-progress, please be patient while we are preparing for the first release in the new organization.
 
+## Migration to the new provider
+
+To migrate from `mrparkers/keycloak` to the `keycloak/keycloak` Terraform provider, you can use the `terraform state replace-provider` command:
+```
+terraform state replace-provider mrparkers/keycloak keycloak/keycloak
+```
+You can find the documentation for this command [here](https://developer.hashicorp.com/terraform/cli/commands/state/replace-provider).
+
 ## Docs
 
 All documentation for this provider can now be found on the Terraform Registry: https://registry.terraform.io/providers/keycloak/keycloak/latest/docs