chore: schemastore conversion script

[henryiii]

This is the script I'm using to prepare the schema for SchemaStore:

SchemaStore/schemastore#3307

When producing that, I've applied #117 and #116 as well.

[abravalheri]

Thank you very much! Should we add a test to make sure all changes in the schemas will always generate a SchemaStore-compliant script after the pre-processing? Is that something relatively easy to achieve?

[henryiii]

Hmm, actually, it probably could be set up in CI pretty easily. The procedure is something like:

git checkout <schemastore>
git checkout <validate-pyproject>
cd validate-pyproject
./tools/to_schemastore.py src/validate_pyproject/plugins/setuptools.schema.json > ../schemastore/src/schemas/json/setuptools.json
cd ../schemastore/src
npm install
npm run grunt # -- --SchemaName=pyproject.json
# Note: checking just one schema (commented above) doesn't seem to work as well