Add canNodeHaveChildren to props list in readme

Author: Kyle Saxberg

README.md

@@ -106,6 +106,7 @@ export default class Tree extends Component {
 | rowDirection                   |     string     | Adds row direction support if set to `'rtl'` Defaults to `'ltr'`.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
 | canDrag                        |  func or bool  | Return false from callback to prevent node from dragging, by hiding the drag handle. Set prop to `false` to disable dragging on all nodes. Defaults to `true`. <div>`({ node: object, path: number[] or string[], treeIndex: number, lowerSiblingCounts: number[], isSearchMatch: bool, isSearchFocus: bool }): bool`</div>                                                                                                                                                                                                                                                                                                                        |
 | canDrop                        |      func      | Return false to prevent node from dropping in the given location. <div>`({ node: object, prevPath: number[] or string[], prevParent: object, prevTreeIndex: number, nextPath: number[] or string[], nextParent: object, nextTreeIndex: number }): bool`</div>                                                                                                                                                                                                                                                                                                                                                                                      |
+| canNodeHaveChildren            |      func      | Function to determine whether a node can have children, useful for preventing hover preview when you have a `canDrop` condition. Default is set to a function that returns `true`. Functions should be of type `(node): bool`.
 | theme                          |     object     | Set an all-in-one packaged appearance for the tree. See the [Themes](#themes) section for more information.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
 | searchMethod                   |      func      | The method used to search nodes. Defaults to [`defaultSearchMethod`](https://github.com/frontend-collective/react-sortable-tree/blob/master/src/utils/default-handlers.js), which uses the `searchQuery` string to search for nodes with matching `title` or `subtitle` values. NOTE: Changing `searchMethod` will not update the search, but changing the `searchQuery` will.<div>`({ node: object, path: number[] or string[], treeIndex: number, searchQuery: any }): bool`</div>                                                                                                                                                               |
 | searchQuery                    | string or any  | Used by the `searchMethod` to highlight and scroll to matched nodes. Should be a string for the default `searchMethod`, but can be anything when using a custom search. Defaults to `null`.                                                                                                                                                                                                                                                                                                                                                                                                                                                        |