Add example for decoding custom errors from JSON-RPC reverts

[zerosnacks]

Related: alloy-rs/alloy#1098 + https://github.com/alloy-rs/alloy/pull/1098/files

See:

    fn custom_error_decoding() {
        sol!(
            library Errors {
                error SomeCustomError(uint256 a);
            }
        );

        let json = r#"{"code":3,"message":"execution reverted: ","data":"0x810f00230000000000000000000000000000000000000000000000000000000000000001"}"#;
        let payload: ErrorPayload = serde_json::from_str(json).unwrap();

        let Errors::ErrorsErrors::SomeCustomError(value) =
            payload.as_decoded_error::<Errors::ErrorsErrors>(false).unwrap();

        assert_eq!(value.a, U256::from(1));
    }

Likely best placed in the contracts as jsonrpc_error_decoding?

[PraneshASP]

The attached code snippet looks good enough for the example. can we just add the same as example or do you prefer a more complex one?

[zerosnacks]

I think we can just add this as an example

[PraneshASP]

Looks like the change (as_decoded_error()) hasn't been released/published yet. will add this after the next release of alloy.

[zerosnacks]

https://github.com/alloy-rs/alloy/releases/tag/v0.2.1 was just released, removing the blocked tag :)