Feature: Allow offline signing of zkApp transactions

[garethtdavies]

For those looking to send multiple transactions before the first is included or signing offline and sending at a later date, it would be useful to be able to manually specify a nonce for the zkApp transaction.

Perhaps this could be included in the FeePayerSpec as an optional value?

FeePayerSpec = PrivateKey | {
    feePayerKey: PrivateKey;
    fee?: string | number | UInt64 | undefined;
    memo?: string | undefined;
    nonce?: number | UInt32 | undefined;
}

[garethtdavies]

Updated the title to better reflect what I am trying to achieve, and while specifying the nonce is required, there might be additional requirements to allow for this?