Add windows test

.github/workflows/test.yml

@@ -17,3 +17,10 @@ jobs:
       run: HOMEBREW_NO_AUTO_UPDATE=1 brew install jq mbedtls
     - name: make
       run: make test test++
+  windows:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: make
+      run: make make mg_prefix vc98 vc2017 ex
+