Mark the annotations that contain a non-empty popup. Especially useful to identify annotations that are not meant to contain an annotation as shapes or highlights.
Problem: The side review is updated only when the mouse is hovered over it. It should be updated as soon as the content of the popup is changed. To do this the method notifyAnnotationChanges of DocumentPrivate in document.cpp should be made public so that it can be connected to the signal TextChanged of the textEdit in annotwindow.cpp.