Adds a custom ABI for an unverified contract address.
Sort uses ABIs to process contracts. In some circumstances, a contract's
ABI may not be available, such as when the contract is under development and deployed
only to a testnet. In these cases, you can add a custom ABI to Sort.
Custom ABIs are checked against Etherscan and Polygonscan daily to see if the contract
has a verified ABI. If so, the custom ABI will be replaced with the verified ABI.