Ex. 3 Task 3: Add Example of Running Docker Containers Locally

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Task 3 has learners build the front-end and back-end containers and then deploy them to Azure Container Registry. It would be a good idea to include a step earlier to run the containers locally to ensure that everything works correctly. That will help debugging efforts in the event that learners have made a mistake in the process of isolating front-end and back-end code.