Added documentation for engine modules and permissions

[Spoorthy1423]

#4647 Added Document on how and when to add classes/permissions/packages to engine module

-Added markdown and clearly stated requirements

Contains

Brief description of what the PR does like "Fixes #12345"

How to test

Brief description of how to test / confirm this PR before merging

Outstanding before merging

If anything. You can use neat checkboxes! Feel free to delete if not needed

• [ ] Need to consider use case x
• [ ] Still have to adjust the wiki doc
• [ ] Will need translation work