Dockerize this application

[64J0]

Description:

With this PR:

• Add Dockerfile, so people with no Node.js installed in their local environments can simply create a Docker container to run the migration process;
• Update the README with usage instructions for the Dockerfile;
• Add .dockerignore to avoid copying some files to the container;
• Add Makefile to make it easier to run the Docker commands.

Let me know if there is anything you guys would like to change. I have tested this locally and it worked fine.