getApproved(contract, nftIdx)

Feature	Return the address of the approved account for NFT with given NFT Idx.
Parameters	string contract address, int nftIdx,
data of SuccessResponse	string address

example

const contractAddress = "0x41EFb6902ADcb1214a7123b01af66b1D13b89864fca";
const nftIdx = 0;

// Note: an asynchronous request.
const NFTInfo = async () => {
    const info = await mitum.nft.getApproved(contractAddress, nftIdx);
    console.log(info.data);
};

NFTInfo();

// output
3a9ooHpDo2MTLcNS6MJKjFeYv59zFyfzm6f3cVVihBZTmca