ci: add demo workflow for testing ghar

see IOXTD-3095

.github/workflows/demo.yml

@@ -0,0 +1,48 @@
+name: Demo
+
+on:
+  workflow_dispatch:
+    inputs:
+      name:
+        description: 'Person or thing to greet'
+        default: 'world'
+        required: true
+        type: string
+      pause:
+        description: 'Pause workflow run for 5m after printing greeting'
+        default: false
+        required: false
+        type: boolean
+      runners:
+        description: 'Runners on which to execute workflow'
+        required: true
+        default: 'arc-dev-runners'
+        type: choice
+        options:
+          - ubuntu-latest
+          - developer-website-arc-dev-runners-adcce
+
+jobs:
+  greet-on-ubuntu-latest:
+    if: inputs.runners == 'ubuntu-latest'
+    runs-on: ubuntu-latest
+    steps:
+    - name: Print greeting
+      run: echo "Hello ${{ inputs.name }} from ${{ inputs.runners }}!"
+
+    - name: Sleep for 5m
+      if: inputs.pause == true
+      run: sleep 300
+
+  greet-on-developer-website-arc-dev-runners-adcce:
+    if: inputs.runners == 'developer-website-arc-dev-runners-adcce'
+    runs-on: developer-website-arc-dev-runners-adcce
+      group: adp-platform-operations
+      labels: arc-dev-runners-corp
+    steps:
+    - name: Print greeting
+      run: echo "Hello ${{ inputs.name }} from ${{ inputs.runners }}!"
+
+    - name: Sleep for 5m
+      if: inputs.pause == true
+      run: sleep 300