Add documentation / guide on how to create a new app environment

[mkleszcz]

Documentation is

• Missing
• Outdated
• Confusing
• Not sure?

Explain in detail

At the moment there is no comprehensive documentation on how to create a new custom environment.
Creating environment with a name different than: dev|qa|prod by only setting environment variables and deployment CI/CD pipelines won't work because workers will fail to deploy because of the misconfiguration in the serverless.yml file.

Your Suggestion for Changes

Prepare a coprehensive guide that will guide through the process of creating a new environment. It should cover setting up the environment variables, deploy infrastructure and make any code change that is needed.