Add retro theme

.github/workflows/deploy-retro.yml

@@ -0,0 +1,31 @@
+name: Deploy Hugo site to Retro Production
+
+on:
+  # Runs on pushes targeting the default branch
+  push:
+    branches:
+      - '*'
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "retro-pages"
+  cancel-in-progress: false
+
+jobs:
+  # Deployment job
+  deploy:
+    environment:
+      name: retro-production
+      url: http://retro.leighhack.org
+    runs-on: ubuntu-latest
+    steps:
+      - name: Invoke deployment hook
+        uses: distributhor/workflow-webhook@v3
+        with:
+          webhook_url: ${{ vars.WEBHOOK_URL }}
+          webhook_secret: ${{ secrets.WEBHOOK_SECRET }}
+          max_time: 300