Add GitHub action for publishing to PyPI (#18)

.bumpversion.cfg

@@ -6,3 +6,4 @@ tag_name = v{new_version}-{now:%Y%m%d}
 
 [bumpversion:file:pyconfs/__init__.py]
 
+[bumpversion:file:.github/workflows/publish_to_pypi.yml]

.github/workflows/publish_to_pypi.yml

@@ -0,0 +1,28 @@
+name: Publish to PyPI
+
+on:
+  push:
+    tags:
+      - v0.5.2(-[0-9]+)?
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+
+      - name: "Installs dependencies"
+        run: |
+          python -m pip install flit
+
+      - name: "Build and publish to PyPI"
+        run: |
+          python -m flit publish
+        env:
+          FLIT_USERNAME: __token__
+          FLIT_PASSWORD: ${{ secrets.PYPI_TOKEN }}