Included new fields

We've added "links" field (e.g. homepage, twitter, discord) to these NFT endpoints responses:

/nfts/{id}
/nfts/{asset_platform}/contract/{contract_address}

Example of responses:

{
  "id": "pudgy-penguins",
  "contract_address": "0xBd3531dA5CF5857e7CfAA92426877b022e612cf8",
  .......
  "links": {
    "homepage": "https://www.pudgypenguins.com/", 👈
    "twitter": "https://twitter.com/pudgypenguins",👈
    "discord": "https://discord.gg/pudgypenguins" 👈
  },
	.......
}