Prepare the app to be deployed to Heroku

[paulomarg]

WHY are these changes introduced?

We're adding support for deploying this app to Heroku using the CLI, and that requires a few things to be put in place.

WHAT is this pull request doing?

• Sets up a Heroku Procfile that prepares the app to run with nginx
• Sets up a proper nginx config file for Heroku
• Added a new npm build script which just builds the React assets
• Sets up apps to run the db migrations (only after the DB has been configured) as part of the release process

Checklist

• I have added/updated tests for this change

[MuhammadFarag]

💪