fix: cosmic_container tag method

src/widget/cosmic_container.rs

@@ -140,6 +140,10 @@ where
         self.container.children()
     }
 
+    fn tag(&self) -> iced_core::widget::tree::Tag {
+        self.container.tag()
+    }
+
     fn diff(&mut self, tree: &mut Tree) {
         self.container.diff(tree);
     }