Use extended format in CarbonNormalizer

[bastianschwarz]

Hey there,

I'm using the event sourcing for building logs for outgoing reqeuests. They are grouped together and since multiple can happen within one second they are currenty "out of sequence" because the CarbonNormalizer noramlizes to seconds ...

Before I create an Issue/PR: Would it hurt if it used the extended format?

    public function normalize(mixed $object, string $format = null, array $context = []): string
    {
        if (! $object instanceof CarbonInterface) {
            throw new InvalidArgumentException('Cannot serialize an object that is not a CarbonInterface in CarbonNormalizer.');
        }

        return $object->toRfc3339String();
    }

becomes

    public function normalize(mixed $object, string $format = null, array $context = []): string
    {
        if (! $object instanceof CarbonInterface) {
            throw new InvalidArgumentException('Cannot serialize an object that is not a CarbonInterface in CarbonNormalizer.');
        }

        return $object->toRfc3339String(true);
    }

(I think that should to the trick)