ci / break unittest job into small job files

.github/workflows/unittest_windows.yml

@@ -0,0 +1,17 @@
+name: windows
+on:
+  push:
+    paths-ignore:
+    - 'docs/**'
+
+jobs:
+  windows:
+    runs-on: windows-latest
+    steps:
+    - uses: actions/checkout@v1
+    - uses: seanmiddleditch/gha-setup-vsdevenv@master
+    - run: |
+        mkdir build
+        cd build
+        cmake -DCMAKE_CXX_COMPILER=cl.exe -DUSE_WS=1 -DUSE_TEST=1 ..
+    - run: cmake --build build