add a new item to an artifact (Auth policies: artifact:modify)

Example response

{
  "images": [
    {
      "folderName": "2017-08",
      "storedFileName": "85007253-09f2-4434-8b7e-1a23db2cd9c9.png",
      "normalSizeImageStoredFileName": "\r\n            e0d7050a-7e30-4a2f-b181-0daa4a1e1068.jpg\r\n            ",
      "thumbnailImageStoredFileName": "\r\n            fbe9cc8e-12fa-4cb9-8f09-bbf353333383.jpg\r\n            "
    }
  ]
}