manual iteration documentation is revised

Author: orxfun

README.md

@@ -78,6 +78,8 @@ We can also walk the tree freely using methods to traverse the links in differen
 * [`node.child(child_idx)`](https://docs.rs/orx-tree/latest/orx_tree/trait.NodeRef.html#method.child), [`node.children()`](https://docs.rs/orx-tree/latest/orx_tree/trait.NodeRef.html#method.children), [`node.children_mut()`](https://docs.rs/orx-tree/latest/orx_tree/trait.NodeRef.html#method.children_mut), [`node.into_child_mut(child_idx)`](https://docs.rs/orx-tree/latest/orx_tree/struct.NodeMut.html#method.into_child_mut)
 * [`node.parent()`](https://docs.rs/orx-tree/latest/orx_tree/trait.NodeRef.html#method.parent), [`node.into_parent_mut()`](https://docs.rs/orx-tree/latest/orx_tree/struct.NodeMut.html#method.into_parent_mut), etc.
 
+Another way to create a custom iterator is simply calling [`node.custom_walk(next_node)`](https://docs.rs/orx-tree/latest/orx_tree/trait.NodeRef.html#method.custom_walk) where the argument `next_node` is a function with pseudo-signature `Fn(Node) -> Option<Node>` and defines the traversal strategy.
+
 *You may see the [manual iteration](https://github.com/orxfun/orx-tree/blob/main/examples/manual_iteration.rs) example that demonstrates different ways to walk the tree with traversal variants (`cargo run --example manual_iteration`).*
 
 ### Arbitrary Order Iterators