add tests for windows

.github/workflows/test.yml

@@ -10,8 +10,8 @@ jobs:
 
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest]
-        python: [3.7, 3.8]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python: [3.7]
 
     steps:
       - uses: actions/checkout@v2