GH Actions multiple Python versions (#86)

Author: femueller

.github/workflows/python-app.yml

@@ -10,12 +10,15 @@ jobs:
 
     runs-on: ubuntu-latest
 
+    strategy:
+      matrix:
+        python-version: [3.5, 3.6, 3.7, 3.8]
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.8
+    - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.8
+        python-version: ${{ matrix.python-version }}
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip