Add CI run on macos (#92)

Author: ianthomas23

.github/workflows/test.yml

@@ -16,7 +16,11 @@ defaults:
 jobs:
   test:
     name: 'Build and test'
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
     steps:
       - name: Checkout source
         uses: actions/checkout@v6