Creates a retrospective process group step

curl --request POST \
  --url https://api.rootly.com/v1/retrospective_process_groups/{retrospective_process_group_id}/steps \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '{
  "data": {
    "type": "retrospective_process_group_steps",
    "attributes": {
      "retrospective_step_id": "<string>",
      "position": 123
    }
  }
}'

{
  "data": {
    "id": "cbff22d8-ad97-4227-9618-ad18b4596b78",
    "type": "retrospective_process_group_steps",
    "attributes": {
      "retrospective_process_group_id": "dd7d715f-a9c1-435c-ab55-ba3c3a139850",
      "retrospective_step_id": "20742287-9719-4115-8aaa-0a14f3517dac",
      "position": 1,
      "updated_at": "2025-11-06T13:28:51.792-08:00",
      "created_at": "2025-11-06T13:28:51.792-08:00"
    }
  }
}