github: add release action

This publishes the Python package to PyPI when a release is created on
GitHub.

Author: dlech

.github/workflows/release-to-pypi.yml

@@ -0,0 +1,22 @@
+name: Release to PyPI
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  build_and_publish:
+    runs-on: ubuntu-20.04
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    - uses: abatilo/actions-poetry@v2.0.0
+      with:
+        poetry-version: 1.1.6
+    - run: poetry install
+    - run: poetry build
+    - run: poetry publish
+      env:
+        POETRY_PYPI_TOKEN_PYPI: ${{ secrets.PYPI_TOKEN }}