Create a Figma attachment

curl "https://api.phrase.com/v2/projects/:project_id/figma_attachments" \
  -u USERNAME_OR_ACCESS_TOKEN \
  -X POST \
  -F branch=my-feature-branch \
  -F url=https://figma.com/file/xxxxx/sample \

{
  "id": "626ea67628690c73ac86ac81eec2d185",
  "url": "https://figma.com/file/something",
  "created_at": "2017-01-28T09:52:53Z",
  "updated_at": "2017-01-28T09:52:53Z"
}