Add PyPI upload workflow

Author: ChristopherMayes

.github/workflows/pypi_upload.yml

@@ -0,0 +1,37 @@
+name: Publish Python distributions to PyPI
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  build-n-publish:
+    if: ${{ github.repository == 'ChristopherMayes/pysuperfish' }}
+    name: Build and publish Python distributions to PyPI
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Set up Python 3.7
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.7
+      - name: Install pypa/build
+        run: >-
+          python -m
+          pip install
+          build
+          --user
+      - name: Build a source tarball
+        run: >-
+          python -m
+          build
+          --sdist
+          --outdir dist/
+          .
+      - name: Publish a Python distribution to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          password: ${{ secrets.PYPI_API_TOKEN }}