feat: error signature utils

[0xpolarzero]

viem exposes utils for converting ABI items, e.g. functions or events, to to a hex signature representation. This is not the case for errors (AbiError), although the underlying logic is present and only needs a wrapper with the right type.

We already have:

• toEventSignature / toFunctionSignature -> toSignature;
• toEventSelector / toFunctionSelector -> toSignatureHash;
• toEventHash / toFunctionHash -> toSignatureHash.

Similarily, the api could expose some new utils:

• toErrorSignature -> toSignature;
• toErrorSelector -> toSignatureHash;
• toErrorHash -> toSignatureHash.

[jxom]

We can expose. Check out https://oxlib.sh/api/AbiItem while you wait. :P

[0xpolarzero]

Oh that's amazing. I had no idea it existed, my bad for not skimming through ox yet.

Might not be worth the hassle then, feel free to close!