add_titled
Description:
Adds a child to this.
The child is identified by the name. The title will be used by [class@ViewSwitcher] to represent child, 
      so it should be short.
Parameters:
| this | a view stack | 
| child | the widget to add | 
| name | the name for  | 
| title | a human-readable title for  | 
Returns:
| the `AdwViewStackPage` for  |