Add how to exclude image

What does this MR do?

Identify the gap in our docs on how to exclude certain images.

Why was this MR needed?

Customer opened an internal ticket asking about how to exclude images as they could not find it in the docs

What's the best way to test this MR?

What are the relevant issue numbers?

I found through Docs for filter of allowed_images are incorrect (#29488) and codebase that we are indeed using doublestar module.