notifications: add modal function for clearing all (#1082)

quickshell/Modals/NotificationModal.qml

@@ -57,6 +57,10 @@ DankModal {
         }
     }
 
+    function clearAll() {
+        NotificationService.clearAllNotifications();
+    }
+
     modalWidth: 500
     modalHeight: 700
     backgroundColor: Theme.withAlpha(Theme.surfaceContainer, Theme.popupTransparency)
@@ -104,6 +108,11 @@ DankModal {
             return "NOTIFICATION_MODAL_TOGGLE_DND_SUCCESS";
         }
 
+        function clearAll(): string {
+            notificationModal.clearAll();
+            return "NOTIFICATION_MODAL_CLEAR_ALL_SUCCESS";
+        }
+
         target: "notifications"
     }