Add "Append" button and "Remove" button for TreeNode or Menu.

[fengshengde]

• I have searched the issues of this repository and believe that this is not a duplicate.

What problem does this feature solve?

Add "Append" button and "Remove" button for TreeNode or Menu. I can edit the TreeNode
like this http://element-cn.eleme.io/#/zh-CN/component/tree#tree-shu-xing-kong-jian

What does the proposed API look like?

<TreeNode title="parent 0" key="0-0">
	<TreeNode title="leaf 0-0" key="0-0-0" isLeaf  editText="edit" deleteText="delete"  editAction="{this.edit()}  deleteAction="{this.delete()}"/>
	<TreeNode title="leaf 0-1" key="0-0-1" isLeaf />
	<Add title = "Append" onClick="{this.add()}"/>
</TreeNode>

[afc163]

title could be a ReactNode.

[damaohub]

title could be a ReactNode.
Can it get the information(key etc) of the selected target?

[daiyang123456]

setTimeout 0;

[keithlimmontajes]

same issue anyone get this ?

[keithlimmontajes]

could not get the selected target info.