multi OS support added to main.yml

.github/workflows/main.yml

@@ -9,7 +9,11 @@ jobs:
   build:
 
     # we can also specify the OS to run tests on
-    runs-on: mint-latest
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: [3.7, 3.8, 3.9, '3.10']
 
     # a job is a seq of steps
     steps:
@@ -19,10 +23,10 @@ jobs:
     - name: Checkout repository
       uses: actions/checkout@v2
 
-    - name: Set up Python 3.9
+    - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.9
+        python-version: ${{ matrix.python-version }}
 
     - name: Install Python dependencies
       run: |