What image types are supported in "Add an idea"?

When I go to add images in a feature request under "Add an idea", I get the following errors:

I cannot find doc on this. I have also tried the Insert function and used multiple browsers (Firefox, Chrome) and in private/incognito modes.

Obviously these image types work when I "ask a question", just not "Add an idea". The above image is a .jpg and those images listed there are below.