validation errors on drafts when running mlcroissant validate --jsonld

[pdurbin]

When I run mlcroissant validate --jsonld src/test/resources/draft/out/croissant.json I get the following error:

E1120 12:11:09.643320 8594579776 validate.py:55] Found the following 1 error(s) during the validation:
  -  [Metadata(Draft Dataset)] ValueError({'Dates or DateTimes should follow the [ISO 8601 format](https://en.wikipedia.org/wiki/ISO_8601). Got '})
Found the following 2 warning(s) during the validation:
  -  [Metadata(Draft Dataset)] Property "https://schema.org/datePublished" is recommended, but does not exist.
  -  [Metadata(Draft Dataset)] WarningException("Version doesn't follow MAJOR.MINOR.PATCH: DRAFT. For more information refer to: https://semver.org/spec/v2.0.0.html")

This is for both mlcroissant==1.0.17 and .22, which I'm playing with in this PR:

• add samplingRate, upgrade to mlcroissant==1.0.22 #29

I'm sure this was introduced when I added support for drafts in this PR:

• handle drafts #14

I guess I didn't validate the JSON? Not sure.

Here's how the error looks at https://huggingface.co/spaces/JoaquinVanschoren/croissant-checker