serializeU64 method
Implementation
void serializeU64(BigInt value) {
checkNumberRange(value, BigInt.zero, MAX_U64_BIG_INT);
final low = value & BigInt.from(MAX_U32_NUMBER);
final high = value >> 32;
// write little endian number
serializeU32(low.toInt());
serializeU32(high.toInt());
}