added os matrix testing

Author: btr1975

.github/workflows/test-bake.yml

@@ -22,7 +22,7 @@ on:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         python-version:
@@ -31,6 +31,10 @@ jobs:
           - '3.10'
           - '3.11'
           - '3.12'
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
 
     steps:
     - uses: actions/checkout@v3