Mention the nessesity to use retrocompat- with older Keycloak versions

src/bin/keycloakify/generateStartKeycloakTestingContainer.ts

@@ -30,6 +30,7 @@ export function generateStartKeycloakTestingContainer(params: { jarFilePath: str
         Buffer.from(
             [
                 "#!/usr/bin/env bash",
+                `# If you want to test with Keycloak version prior to 23 use the retrocompat-${pathBasename(jarFilePath)}`,
                 "",
                 `docker rm ${containerName} || true`,
                 "",