Add workflow

Author: swinton

.github/workflows/main.yml

@@ -0,0 +1,20 @@
+name: Hello World
+
+on:
+  workflow_call:
+
+jobs:
+  hello-world:
+    name: Hello World
+    runs-on: ubuntu-latest
+    steps:
+    - name: Context
+      env:
+        GITHUB_CONTEXT: ${{ toJson(github) }}
+      run: |
+        echo "$GITHUB_CONTEXT"
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Hello World
+      run: |
+        echo "Hello World"