Generate digital attestations for PyPI (PEP 740)

Author: hugovk

.github/workflows/publish.yml

@@ -31,3 +31,5 @@ jobs:
     - name: Publish distribution 📦 to PyPI
       if: startsWith(github.event.ref, 'refs/tags') || github.event_name == 'release'
       uses: pypa/gh-action-pypi-publish@release/v1
+      with:
+        attestations: true