Add object to the this object pool so it can be referenced just like any other object
built by builder.
Only a single object may be added using name. However, it is not an error to expose the same object under multiple names.
`gtk_builder_get_object()` may be used to determine if an object has already been added with name.
| this |
a `GtkBuilder` |
| name |
the name of the object exposed to the builder |
| object |
the object to expose |