Add toErrorSelector utility

[Destiner]

Similar to toFunctionSelector and toEventSelector, consider adding a utility function that takes AbiError and outputs Hex.

Reference implementation:

function toErrorSelector(abi: AbiError): Hex {
  return slice(keccak256(toHex(formatAbiItem(abi))), 0, 4);
}

Additionally, consider exposing AbiError from abitype and adding toErrorSignature (similar to toFunctionSignature)