Add GitHub workflow

.github/workflows/package.yml

@@ -0,0 +1,57 @@
+name: Test & publish
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+  release:
+    types: [created]
+
+jobs:
+  build:
+    name: Python ${{ matrix.python-version }} / ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      max-parallel: 9
+      fail-fast: false
+      matrix:
+        python-version: [3.6, 3.7, 3.8]
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install poetry
+        poetry install
+    - name: Test with pytest
+      run: |
+        poetry run pytest --color=yes
+
+  publish:
+    name: Publish to PyPI
+    runs-on: ubuntu-latest
+    needs: build
+    if: github.event_name == 'release'
+    steps:
+      - uses: actions/checkout@v1
+      - name: Set up Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: '3.8'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install poetry
+      - name: Build and publish
+        env:
+          PYPI_USERNAME: ${{ secrets.PYPI_USERNAME }}
+          PYPI_PASSWORD: ${{ secrets.PYPI_PASSWORD }}
+        run: |
+          poetry publish --build -u $PYPI_USERNAME -p $PYPI_PASSWORD