Document how to customize the document picker for the RTE

We need to document how to customize the document picker for the Web UI's rich text editor.

Make it centered around a real life use case like headless article publishing, potential structure as follows

Using and customizing the rich text editor for article publishing

Use case introduction
What elements can I use?
How to retrieve the content in my external system?
How do I reference images in my article?
How do I keep track of which images are being used in my articles?