message: Add to Boxel::Menu docs
diff: <:api as |Args|>
  <Args.Object
  @name="items"
  - @description="An array of MenuItems, created using the `menu-item` helper."
  + @description="An array of MenuItems, created using the `menu-item` helper. The menu-item helper accepts the menu item text as its first argument, and an action or link (as created using ember-link) as the second argument."
  />
  <Args.Action
  @name="closeMenu"
  