ci: add GitHub Actions workflow

Author: zah

.github/workflows/ci.yml

@@ -0,0 +1,36 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  tests:
+    name: Tests on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install make on Windows
+        if: runner.os == 'Windows'
+        run: choco install make -y
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+      - name: Run tests
+        shell: bash
+        run: make test
+
+  nix-tests:
+    name: NixOS tests
+    runs-on: ubuntu-latest
+    container:
+      image: nixos/nix:latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run tests in Nix shell
+        run: nix develop --command python -m unittest discover -v