common tree 树结构

通用树结构库， 是现实了深度遍历(preorder, 先序遍历)和广度优先遍历

usage 用法

更多可以查看examples

```rust

use common_tree::Node;

struct NodeData { id: usize, name: String, }

impl NodeData { pub fn new(id: usize, name: String) -> Self { Self { id, name, } }

pub fn print(&self) {
    println!("id: {}, name: {}", self.id, self.name);
}

} type HellNode = Node;

fn main() {

let root = HellNode::new(NodeData::new(0, format!("root")));

root.data().print();

}

```

run examples

cargo run --example hello