Update passing string as error with object

[oa-s]

instead of using error we need to pass object {message: "error mesage", code: 1}
@hboon could u please make pr to this repo with changes, needs for AlphaWallet/alpha-wallet-ios#6456
we actually need to use
const response = {'id': id, jsonrpc: '2.0', result: value, error: error } instead of
const response = {'id': id, jsonrpc: '2.0', result: value, error: {message: error} }