Tooling: Extract website deploy into own workflow

- Standalone deploy so CI can be disabled temporarily without losing auto-deploy on push to main
- Uses `paths` filter to only trigger on website file changes

Author: vdavid

.github/workflows/deploy-website.yml

@@ -0,0 +1,28 @@
+name: Deploy website
+
+on:
+    push:
+        branches:
+            - main
+        paths:
+            - 'apps/website/**'
+            - '.dockerignore'
+            - 'CHANGELOG.md'
+
+jobs:
+    deploy:
+        name: Deploy website
+        runs-on: ubuntu-latest
+
+        steps:
+            - name: Trigger deploy webhook
+              run: |
+                  # Compute HMAC-SHA256 signature
+                  PAYLOAD='{}'
+                  SIGNATURE=$(echo -n "$PAYLOAD" | openssl dgst -sha256 -hmac "${{ secrets.DEPLOY_WEBHOOK_SECRET }}" | cut -d' ' -f2)
+
+                  # Send signed request to webhook
+                  curl -f -X POST https://getcmdr.com/hooks/deploy-website \
+                    -H "Content-Type: application/json" \
+                    -H "X-Hub-Signature-256: sha256=$SIGNATURE" \
+                    -d "$PAYLOAD"