Implement IntoIterator for references to a BreadcrumbTreeNode.

src/renderer/breadcrumb_tree.rs

@@ -49,3 +49,12 @@ impl<'a> Iterator for BreadcrumbTreeIterator<'a> {
         ret.map(|node| node.get_ice())
     }
 }
+
+impl<'a, C: IntoContextElement> IntoIterator for &'a BreadcrumbTreeNode<'a, C> {
+    type Item = &'a dyn IntoContextElement;
+    type IntoIter = BreadcrumbTreeIterator<'a>;
+
+    fn into_iter(self) -> BreadcrumbTreeIterator<'a> {
+        BreadcrumbTreeIterator(Some(self))
+    }
+}