Deploy to demo app on merges

Author: lorenyu

.github/workflows/cd.yml

@@ -21,6 +21,8 @@ jobs:
             app: app-rails
           - repo: navapbc/pfml-starter-kit-app
             app: paidleave
+          - repo: navapbc/pfml-starter-kit-app
+            app: demo
     steps:
       - name: Checkout project repo
         uses: actions/checkout@v4