Add an example to use the auto id feature.

examples/auto_node_id/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "auto_node_id"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+tree-ds = { path = "../../../tree-ds", features = ["auto_id"] }

examples/auto_node_id/src/main.rs

@@ -0,0 +1,21 @@
+use tree_ds::prelude::*;
+
+fn main() {
+    let mut tree = Tree::<AutomatedId, &str>::new(Some("Sample Tree"));
+    let ceo_node = tree
+        .add_node(Node::new_with_auto_id(Some("CEO")), None)
+        .unwrap();
+    let _coo_node = tree
+        .add_node(Node::new_with_auto_id(Some("COO")), Some(&ceo_node))
+        .unwrap();
+    let _cto_node = tree
+        .add_node(Node::new_with_auto_id(Some("CTO")), Some(&ceo_node))
+        .unwrap();
+    let _cfo_node = tree
+        .add_node(Node::new_with_auto_id(Some("CFO")), Some(&ceo_node))
+        .unwrap();
+    let _cio_node = tree
+        .add_node(Node::new_with_auto_id(Some("CIO")), Some(&ceo_node))
+        .unwrap();
+    println!("{}", tree);
+}