Update README.md

Author: MichelLeBon

jackson/README.md

@@ -15,3 +15,4 @@
 - [Jackson – Working with Maps and nulls](http://www.baeldung.com/jackson-map-null-values-or-null-key)
 - [Jackson – Decide What Fields Get Serialized/Deserializaed](http://www.baeldung.com/jackson-field-serializable-deserializable-or-not)
 - [A Guide to Jackson Annotations](http://www.baeldung.com/jackson-annotations)
+- [Working with Tree Model Nodes in Jackson](http://www.baeldung.com/jackson-json-node-tree-model)