add_item
Description:
Adds a new resource, pointed by uri, into the recently used resources list.
This function automatically retrieves some of the needed metadata and setting other metadata to common default values; it then feeds the data to [method@Gtk.RecentManager.add_full].
See [method@Gtk.RecentManager.add_full] if you want to explicitly define the metadata for the resource pointed by uri.
Parameters:
| this | a `GtkRecentManager` | 
| uri | a valid URI | 
Returns:
| true if the new item was successfully added to the recently used resources list |