add branches

.github/workflows/ci.yml

@@ -0,0 +1,24 @@
+on:
+  push:
+    branches:
+      - master
+      - Set-up-GHA-CI/CD
+      
+  pull_request:
+
+jobs:
+  validate:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        # os: [windows-latest]
+        # os: [windows-latest, ubuntu-18.04]
+        os: [windows-latest, ubuntu-latest, macos-latest]
+        # os: [ubuntu-18.04]
+    steps:
+    - uses: actions/checkout@v1      
+    - name: Run Continuous Integration
+      shell: pwsh
+      run : |
+        # ./ContinuousIntegration/ContinuousIntegration.ps1
+        "Hello World"