Sets the title for the `GtkHeaderBar`.
When set to null, the headerbar will display the title of the window it is contained in.
The title should help a user identify the current view. To achieve the same style as the builtin title, use the “title” style class.
You should set the title widget to null, for the window title label to be visible again.
| this |
a `GtkHeaderBar` |
| title_widget |
a widget to use for a title |