Build demo application: hello world with background color and display image.

• Build docker file: docker build -t <YOUR_DOCKER_USERNAME>/concepts-build-image-demo:tag .
• Push the image: docker push <YOUR_DOCKER_USERNAME>/concepts-build-image-demo:tag

After creating the image and pushing it to the container registry, Look at hello-world-color (https://github.com/SE-I-T-Digital/hello-world-color/tree/main) to deploy it.