GitHub Actions: Do we want an OS and Python build matrix?

Related to multi-build#434 and multi-build#435

.github/workflows/test.yml

@@ -17,17 +17,28 @@ on:
 jobs:
   # This workflow contains a single job called "build"
   build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]       # [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ["3.10"]  # ["2.7", "3.7", "3.8", "3.9", "3.10", "3.11", "pypy3"]
+
     # The type of runner that the job will run on
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
 
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
       - uses: actions/checkout@v2
 
+      - uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python-version }}
+
       # Runs a single command using the runners shell
       - name: Run a one-line script
-        run: echo Hello, world!
+        shell: python
+        run: print("Hello, world!")
 
       # Runs a set of commands using the runners shell
       - name: Run a multi-line script