[Improvement] Add documentation for usage of release scripts

### What would you like to be improved?

The release scripts have no documentation, at a minimum they should list all the required environment variables and explain what they are for and the format they need to be in.

### How should we improve?

Add some documentation for the release scripts.

Start by locating the release scripts and identifying every environment variable they require. Document each variable's purpose and expected format alongside the release-script documentation; the work is done when users can understand and configure all required variables.

Written by the indexing model from the issue text.