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": "2720ef0d-c099-4463-9e1b-1e55cb9a19df",
    "type": "retrospective_process_group_steps",
    "attributes": {
      "retrospective_process_group_id": "2eb7a1e0-47c5-4500-a02b-2d8821877bbb",
      "retrospective_step_id": "7914c1da-e4c9-44b6-809b-845e30ebbee6",
      "position": 1,
      "updated_at": "2025-03-20T17:53:36.793-07:00",
      "created_at": "2025-03-20T17:53:36.793-07:00"
    }
  }
}