Add PyPI publishing workflow

[abdellatifLabr]

Summary

• Adds GitHub Actions workflow to publish package to PyPI on tag push

Workflow Details

• Trigger: Runs when a git tag matching v*.*.* is pushed (e.g., v0.2.0)
• Authentication: Uses Trusted Publishing (OIDC) - no API tokens in secrets
• Build: Uses python -m build with setuptools

How to Publish

1. Update version in pyproject.toml
2. Create and push a tag:

   git tag v0.2.0
   git push origin v0.2.0

Setup Required

Before first publish, configure Trusted Publishing on PyPI:

• Go to https://pypi.org/manage/account/publishing/
• Add publisher with:
  • Project name: jsonldb
  • Owner: your GitHub username/org
  • Repository: jsonldb
  • Workflow: publish.yml
  • Environment: create pypi environment in repo settings