Replace GitLab CI with Github workflow

Author: jaraco

.github/workflows/main.yml

@@ -0,0 +1,42 @@
+name: Automated Tests
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        python: [3.6, 3.8, 3.9]
+        platform: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python }}
+      - name: Install tox
+        run: |
+          python -m pip install tox
+      - name: Run tests
+        run: tox
+
+  release:
+    needs: test
+    if: github.event_name == 'push' && contains(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - name: Install tox
+        run: |
+          python -m pip install tox
+      - name: Release
+        run: tox -e release
+        env:
+          TWINE_PASSWORD: ${{ secrets.PYPI_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}