Add PyPI trusted publishing workflow

- Publishes to Test PyPI for every commit to main
- Publishes to PyPI for version tags

.github/workflows/pypi-package.yml

@@ -0,0 +1,63 @@
+---
+name: PyPI package
+
+on:
+  push:
+    branches: [main]
+    tags: ["v[0-9]+.[0-9]+.[0-9]+*"]
+  workflow_dispatch:
+
+permissions:
+  attestations: write
+  contents: read
+  id-token: write
+
+jobs:
+  package:
+    name: Build & verify package
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0 # needed for setuptools_scm version determination
+      # HACK: for now, disable local versions so we can push to Test PyPI on main
+      - name: Disable local version
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+        run: |
+          sed -i '/\[tool\.setuptools_scm\]/a local_scheme = "no-local-version"' pyproject.toml
+          git update-index --assume-unchanged pyproject.toml
+      - uses: hynek/build-and-inspect-python-package@v2
+        with:
+          attest-build-provenance-github: 'true'
+
+  release-test-pypi:
+    name: Publish dev package to test.pypi.org
+    if: github.repository_owner == 'nickstenning' && github.ref == 'refs/heads/main'
+    runs-on: ubuntu-latest
+    needs: package
+    environment: test-pypi
+    steps:
+      - name: Download packages
+        uses: actions/download-artifact@v4
+        with:
+          name: Packages
+          path: dist
+      - name: Upload package to Test PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          repository-url: https://test.pypi.org/legacy/
+
+  release-pypi:
+    name: Publish released package to pypi.org
+    if: github.repository_owner == 'nickstenning' && startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    needs: package
+    environment: pypi
+    steps:
+      - name: Download packages
+        uses: actions/download-artifact@v4
+        with:
+          name: Packages
+          path: dist
+      - name: Upload package to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1