Documentation: Explain `<image entrypoint>`

In the instructions there are some small pieces left out that make documentation difficult to understand.
This is one piece. What is the image entrypoint? I think it is wise not to assume people reading know what that is.

What are the minimum required ingredients to get this tool working?
What script names do I need to create in order to follow along with the instructions?

Locate the instructions that contain the `` reference and read the surrounding setup steps. Clarify what the image entrypoint means, then document the minimum required ingredients and script names needed to follow the instructions. Done means a reader can identify the required setup without assuming prior knowledge.

Written by the indexing model from the issue text.