[RFC] Menu separator (vertical and horizontal)

[joheredi]

Feature Request

Implement Vertical Divider

Problem description

Stardust already provides a horizontal divider, however, it lacks a vertical divider. Supporting a "vertical" prop would come in handy. For instance to separate menu items in toolbars

[jurokapsiar]

Renamed the issue to specifically address menu. Creating a standalone vertical separator might or might not be a prerequisite.