PEP 739: update fields based on feedback and add JSON Schema

[FFY00]

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📚 Documentation preview 📚: https://pep-previews--3851.org.readthedocs.build/

[FFY00]

@python/pep-editors are my files to update the PEP based on the JSON Schema okay to commit?

[hugovk]

Hmm, I think if they're part of the PEP itself, like example code, they can be in this repo. But helper code for generating parts of the PEP should probably be kept elsewhere.

https://peps.python.org/pep-0001/#auxiliary-files

[FFY00]

Alright, I put them in a gist and added a comment in the .rst file.