Get benchmark indexes

curl --request GET \
  --url https://api.tilt.io/custom/benchmark-indexes/ \
  --header 'X-Api-Key: <api-key>'

[
  {
    "name": "<string>",
    "identifier": "<string>",
    "description": "<string>",
    "composition": {
      "constituents": [
        {
          "ticker": "<string>",
          "weight": "<string>"
        }
      ]
    },
    "constituent_count": 123
  }
]