src/vs/workbench/common/notifications.ts/NotificationsModel/addNotification
class NotificationsModel:	addNotification(notification: INotification): INotificationHandle {
		const item = this.createViewItem(notification);
		if (!item) {
			return NotificationsModel.NO_OP_NOTIFICATION; // return early if this is a no-op
		}

		// Deduplicate
		const duplicate = this.findNotification(item);
		duplicate?.close();

		// Add to list as first entry
		this._notifications.splice(0, 0, item);

		// Events
		this._onDidChangeNotification.fire({ item, index: 0, kind: NotificationChangeType.ADD });

		// Wrap into handle
		return new NotificationHandle(item, item => this.onClose(item));
	}