github: workflow: test: Run on Windows

Added windows-latest to the OS matrix.

Author: stadlero

.github/workflows/test.yml

@@ -4,10 +4,11 @@ on: [push, pull_request]
 
 jobs:
   build-test:
-    runs-on:
-      - ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
 
     steps:
       - name: Setup Python