ci: enable CI builds on proprietary OSes

Author: austinhartzheim

.github/workflows/ci.yml

@@ -5,7 +5,10 @@ name: CI
 jobs:
   check:
     name: Check
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ ubuntu-latest, macos-latest, windows-latest ]
+    runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout sources
         uses: actions/checkout@v3