adding windows CI as github action

Author: mmatera

.github/workflows/windows.yml

@@ -0,0 +1,33 @@
+name: Mathics (Windows)
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: windows-latest
+    strategy:
+      matrix:
+        os: [windows]
+        python-version: [3.6, 3.7, 3.8, 3.9]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        choco llvm
+        python -m pip install --upgrade pip
+        LLVM_CONFIG=/usr/local/Cellar/llvm@9/9.0.1_2/bin/llvm-config pip install llvmlite
+    - name: Install Mathics
+      run: |
+        make develop
+    - name: Test Mathics
+      run: |
+        pip install pytest pexpect
+        make -j3 check