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?

找出包含 `` 參照的說明，並閱讀其周圍的設定步驟。釐清 image entrypoint 的含義，然後記錄遵循這些說明所需的最少必要項目和 script 名稱。完成的標準是讀者不必具備先備知識，就能辨識所需的設定。

由索引模型根據 Issue 內容生成。