Add gh-actions continuous integration

.github/workflows/ci.yml

@@ -0,0 +1,32 @@
+name: continuous-integration
+on: push
+
+env:
+  PROJECT_ROOT: ${{ github.workspace }}
+
+jobs:
+  tests:
+    name: "Python ${{ matrix.python-version }} on ${{ matrix.os }}"
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ["ubuntu-latest", "macos-latest"] 
+        python-version: ["3.9", "3.10", "3.11"]
+
+    steps:
+      - uses: "actions/checkout@v3"
+      - uses: "actions/setup-python@v4"
+        with:
+          python-version: "${{ matrix.python-version }}"
+      - name: "Install package dependencies"
+        run: |
+          python -VV
+          python -m site
+          python -m pip install --upgrade pip setuptools wheel
+          python -m pip install --use-pep517 .  # TODO pep517 flag; see #36
+          python -m pip install --use-pep517 -r requirements.txt  # TODO pep517 flag; see #36
+
+      - name: "Run package tests for ${{ matrix.python-version }}, ${{ matrix.os }}"
+        run: "python -m pytest -vv"