make displayed content types configurable

content types displayed in a folder listing should be configurable
most of the time it doesn't make sense to display images, especially if they are already shown in the content area

The issue identifies folder listings as the entry point but names no file or test. Start by locating the code that builds a folder listing and trace how content types are selected, then look for existing configuration patterns and tests. Done means the displayed types can be configured, including excluding images from the listing.

Written by the indexing model from the issue text.