update CI/CD pipeline: add docker image prune command and log message in app.js

Co-authored-by: Copilot <copilot@github.com>

Author: Wcoder547

.github/workflows/deploy.yml

@@ -46,4 +46,4 @@ jobs:
             cd ~/MERN-CHAT-APP
             docker compose pull
             docker compose up -d --remove-orphans
-            docker image prune -f
+            docker image prune -f

Back-end/app.js

@@ -39,6 +39,8 @@ const onlineUsers = new Set();
 
 connectDB(mongoURI);
 
+console.log("ci/cd pipeline test");
+
 cloudinary.config({
   cloud_name: process.env.CLOUDINARY_CLOUD_NAME,
   api_key: process.env.CLOUDINARY_API_KEY,