[PopupMenu] is a [Control] that displays a list of options. They are popular in toolbars or context menus.
+ The size of a [PopupMenu] can be limited by using [member Window.max_size]. If the height of the list of items is larger than the maximum height of the [PopupMenu], a [ScrollContainer] within the popup will allow the user to scroll the contents.
+ If no maximum size is set, or if it is set to 0, the [PopupMenu] height will be limited by its parent rect.