Gets or sets whether each heading starts with a fold button that hides or shows its section: the
blocks that follow it, up to the next heading of the same or a higher level. Sections start
expanded; the button also answers Enter and Space, and is a Tab stop. Navigating to a heading
(ScrollToAnchor(String)) or a find match in a collapsed section expands it, and hidden
sections are left out of selection and copying. Defaults to false. Can be set from a style,
e.g. for every viewer of an application.
public bool AreHeadingsFoldable { get; set; }