Move the resize handle over between the treeview and the editor

Otherwise it covers up the scrollbar in the treeview. No bueno.

src/packages/tree-view/stylesheets/tree-view.less

@@ -13,7 +13,7 @@
   .tree-view-resize-handle {
     position: absolute;
     top: 0;
-    right: 0;
+    right: -5px;
     bottom: 0;
     width: 10px;
     cursor: col-resize;