chore: publish json schemas as release artifacts

[v-rocheleau]

• new django manage.py script schemas to generate single file JSON-schemas for phenopackets, experiments and discovery
• new release github actions workflow is triggered on new releases and adds the schemas to the release as an artifact zip file

Tested with a dummy pre-release with a PR trigger.
The content of the json-schemas-clean.zip artifact is what it will look like on a real release, but with the json-schemas.zip name (artifacts cannot be overriden, so I changed the names as I was testing to avoid errors).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.99%. Comparing base (5a3da67) to head (4dac651).
Report is 15 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #540   +/-   ##
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  Coverage    90.99%   90.99%           
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  Files          131      131           
  Lines         4939     4939           
  Branches       705      705           
========================================
  Hits          4494     4494           
  Misses         299      299           
  Partials       146      146           

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[davidlougheed]

you can probably fix the errors right now by setting up python, running poetry install before export, and doing poetry run ./manage.py [...] in order to use the poetry env to run the script.

[davidlougheed]

lgtm