Missing defaults for duration_buckets about mojolicious-plugin-prometheus

[tyldum]

Those are the defaults from Net::Prometheus in this case. I'm not sure it's best to document that instead or copypasta the defaults from Net::Prometheus. As it stands not it leaves room for errors, agreed.

[christopherraa]

Perhaps a note on that and where in Net::Prometheus those defaults can be found would be beneficial? Since their documentation does not hold those defaults the best thing might be to link directly to the line in code where it is defined.