Add prepend_mod guides Doc

What does this MR do and why?

Add prepend_mod Guides Document.

Screenshots or screen recordings

Non-UI

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.