Add macOS testing to CI

Windows does not quite work yet, there are a multitude of issues with
cel-cpp that prevent it from functioning :(

.github/workflows/ci.yaml

@@ -12,8 +12,11 @@ permissions:
   contents: read
 jobs:
   test:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
     name: Unit tests
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Cache
         uses: actions/cache@v3
@@ -24,6 +27,9 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 1
+      - name: Install Make
+        run: choco install make
+        if: runner.os == 'Windows'
       - name: Install go
         uses: actions/setup-go@v5
         with: