Typo in readme

[rem-code-s]

I was checking out the DIP721 readme and i think there is a typo, i think this
approveDip721: (user: principal, nat64: token_id) -> (TxReceipt) query;
should be
approveDip721: (user: principal, token_id: nat64) -> (TxReceipt);

Also this function is missing the types i think, cant seem to find it in the code as wel
onDIP721Received: (address caller, address from, uint256 token_id, bytes data) -> ();

[adamspofford-dfinity]

Slightly more importantly, it almost certainly shouldn't be query.

[rem-code-s]

@adamspofford-dfinity you are right, I edited it 👍🏻