Allow to disable or enable the expand/collapse button (#33)

Author: Clézio Alves dos Santos

README.md

@@ -90,6 +90,7 @@ You can get the list of `ISlTreeNode` from the computed `slVueTree.nodes` proper
 |------------------|--------------------|------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | value            | ISlTreeNodeModel[] | []                     | An array of nodes to show. Each node is represented by `ISlTreeNodeModel` interface                                                                                                                              |
 | allowMultiselect | Boolean            | true                   | Disable or enable the multiselect feature                                                                                                                                                                |
+| allowToggleBranch | Boolean            | true                   | Disable or enable the expand/collapse button                                                                                                                                                                |
 | edgeSize         | Number             | 3                      | Offset in pixels from top and bottom for folder-node element. While dragging cursor is in that offset, the dragging node will be placed before or after the folder-node instead of being placed inside the folder. |
 | scrollAreaHeight | Number             | 70                     | Offset in pixels from top and bottom for the component element. While dragging cursor is in that area, the scrolling starts.                                                                                |
 | maxScrollSpeed   | Number             | 20                     | The scroll speed is relative to the cursor position. Defines the max scroll speed.             

dist/sl-vue-tree.d.ts

@@ -34,6 +34,7 @@ export default class SlVueTree<TDataType> extends Vue {
     showBranches: boolean;
     level: number;
     parentInd: number;
+    allowToggleBranch: boolean;
     private rootCursorPosition;
     private rootDraggingNode;
     cursorPosition: ICursorPosition<TDataType>;