chore: auto-open review apps on Heroku (#494)

.github/workflows/review-app.yaml

@@ -0,0 +1,20 @@
+name: Heroku Review App
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize, closed]
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - name: Update Heroku
+        uses: readmeio/heroku-review-app-action@main
+        with:
+          heroku_email: ${{ secrets.HEROKU_EMAIL }}
+          heroku_api_key: ${{ secrets.HEROKU_API_KEY }}
+          pipeline_name: markdown