Add tag-driven PyPI publish workflow

Trusted Publishing via GitHub OIDC: pushing a v* tag runs the test
suite, builds sdist+wheel, and publishes to PyPI through the pypi
environment. No API tokens stored anywhere; PyPI must have the matching
pending publisher configured (project listingsapi, owner synup, repo
listingsapi-python-sdk, workflow publish.yml, environment pypi).

Author: Anirudha2604

.github/workflows/publish.yml

@@ -0,0 +1,32 @@
+name: Publish to PyPI
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - run: pip install -e ".[dev]"
+      - run: pytest
+
+  publish:
+    needs: test
+    runs-on: ubuntu-latest
+    environment: pypi
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+      - run: pip install build
+      - run: python -m build
+      - uses: pypa/gh-action-pypi-publish@release/v1