[add] Action for task b; push to main repo

.github/workflows/build.yml

@@ -0,0 +1,34 @@
+name: Create and push docker image to Docker Hub.
+
+on:
+  push:
+    branches: [ main ]
+
+jobs:
+  docker:
+        
+    runs-on: ubuntu-latest
+
+    steps:
+        - 
+          name: Checkout the code from main branch
+          uses: actions/checkout@v4
+
+        - 
+          name: Login to Docker Hub
+          uses: docker/login-action@v3
+          with:
+            username: ${{ vars.DOCKERHUB_USERNAME }}
+            password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        
+        -
+          name: Set up Docker Buildx
+          uses: docker/setup-buildx-action@v3.9.0
+
+        - 
+          name: Build and push Docker images
+          uses: docker/build-push-action@v6.13.0
+          with:
+            push: true
+            tags: user/main:action
+