add_button
Description:
Adds a button with the given text.
Note: 
      
        
    
    Use [class@Gtk.Window] instead
GTK arranges things so that clicking the button will emit the [signal@Gtk.Dialog:GtkDialog:response] signal with the given 
        response_id. The button is appended to the end of the dialog’s action area. The button widget is returned, but usually you don’t 
      need it.
Parameters:
| this | 
           a `GtkDialog`  | 
      
| button_text | 
           text of button  | 
      
| response_id | 
           response ID for the button  | 
      
Returns:
| 
           the `GtkButton` widget that was added  |