sign method
Implementation
void sign({required ZkLinkSigner zkLinkSigner, dynamic hint}) =>
    RustLib.instance.api
        .fundingSign(that: this, zkLinkSigner: zkLinkSigner, hint: hint);
void sign({required ZkLinkSigner zkLinkSigner, dynamic hint}) =>
    RustLib.instance.api
        .fundingSign(that: this, zkLinkSigner: zkLinkSigner, hint: hint);