added github actions " brain file'' (workflow file)

This sets up automatic CI/CD pipeline:
- Installs Node.js dependencies
- Runs tests and builds the app
- Builds Docker image and pushes to DockerHub
Triggered on every push to main branch.

Author: kishxrx

.github/workflows/main.yml

@@ -0,0 +1,36 @@
+name: CI/CD Pipeline
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Get code
+        uses: actions/checkout@v2
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v3
+        with:
+          node-version: '16'
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run tests
+        run: npm test
+
+      - name: Build app
+        run: npm run build
+
+      - name: Build Docker image
+        run: docker build -t kishxrx/nodejs-demo-app:latest .
+
+      - name: Login to DockerHub
+        run: echo "${{ secrets.DOCKER_PASSWORD }}" | docker login -u "${{ secrets.DOCKER_USERNAME }}" --password-stdin
+
+      - name: Push to DockerHub
+        run: docker push kishxrx/nodejs-demo-app:latest