Add release action:

.github/workflows/release.yml

@@ -0,0 +1,27 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Python 3.8
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+      - name: Build distribution
+        run: |
+          # set version from '${{ github.ref_name }}'
+          export RELEASE_VERSION=${{ github.ref_name }}
+          python setup.py sdist
+      - name: Publish a Python distribution to PyPI
+        if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags')
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          user: __token__
+          password: ${{ secrets.PYPI_API_TOKEN }}