Try tests on Windows and Macs

Author: jeromekelleher

.github/workflows/ci.yml

@@ -17,9 +17,10 @@ jobs:
       - uses: pre-commit/action@v3.0.1
   test:
     name: Test
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
         python-version: ["3.9", "3.10", "3.11"]
     steps:
       - uses: actions/checkout@v4