primeng.d.ts misses export of TreeNode

[jbrekle]

When testing the example for Tree
http://www.primefaces.org/primeng/#/tree

I found that the TreeNode component could not be found when importing it like
import {TreeNode} from 'primeng/primeng';
This probably is because primeng.d.ts misses export of TreeNode

workaround until this is fixed (I guess)
import {TreeNode } from 'primeng/components/api/treenode';