Added treeitem role to tree items. Updated a few devDependencies.

package.json

@@ -33,24 +33,24 @@
   ],
   "devDependencies": {
     "@rollup/plugin-alias": "^2.2.0",
-    "@storybook/addon-notes": "^3.4.11",
-    "@storybook/addon-options": "^3.4.11",
-    "@storybook/vue": "^3.4.11",
+    "@storybook/addon-notes": "^3.4.12",
+    "@storybook/addon-options": "^3.4.12",
+    "@storybook/vue": "^3.4.12",
     "@vue/test-utils": "^1.0.0-beta.25",
     "babel-core": "^6.26.3",
     "babel-jest": "^22.4.4",
     "babel-plugin-transform-builtin-extend": "^1.1.2",
     "babel-preset-env": "^1.7.0",
-    "cross-env": "^5.2.0",
+    "cross-env": "^6.0.3",
     "eslint": "^4.19.1",
     "eslint-plugin-jest": "^21.22.1",
     "eslint-plugin-vue-libs": "^2.1.0",
     "jest": "^22.4.4",
     "rollup": "^0.66.6",
     "rollup-plugin-buble": "^0.19.8",
     "rollup-plugin-serve": "^1.0.1",
-    "rollup-plugin-uglify": "^6.0.3",
-    "rollup-plugin-vue": "4.6.0",
+    "rollup-plugin-uglify": "^6.0.4",
+    "rollup-plugin-vue": "4.6.1",
     "vue": "^2.6.10",
     "vue-jest": "^3.0.5",
     "vue-loader": "^15.7.2",

src/components/TreeNode.vue

@@ -1,5 +1,5 @@
 <template>
-  <li class="tree-node" :data-id="node.id" :class="nodeClass" @mousedown.stop="handleMouseDown">
+  <li role="treeitem" class="tree-node" :data-id="node.id" :class="nodeClass" @mousedown.stop="handleMouseDown">
     <div class="tree-content" :style="[options.direction == 'ltr' ? {'padding-left': padding} : {'padding-right': padding}]" @click.stop="select">
       <i
         class="tree-arrow"