signAsync method
this function must be called after parseQrCode. @return: signature String
Implementation
Future<String?> signAsync(String chain, password) async {
final res = await serviceRoot.webView!
.evalJavascript('keyring.signAsync("$chain", "$password")');
if (res['error'] != null) {
throw Exception(res['error']);
}
return res['signature'];
}