sqrt method

Implementation

@override
FieldSqrtResult<JubJubNativeFr> sqrt() {
  final sqrt = pow(
    BigInt.parse(
      "1638621099222693452482741890880811432426480316468079320341339790598045813550",
    ),
  );
  return FieldSqrtResult(sqrt, (sqrt * sqrt) == this);
}