fix(aria-allowed-role): added gridcell, separator, and treeitem to allowed roles of button element

Author: msereniti

lib/standards/html-elms.js

@@ -140,15 +140,18 @@ const htmlElms = {
     allowedRoles: [
       'checkbox',
       'combobox',
+      'gridcell',
       'link',
       'menuitem',
       'menuitemcheckbox',
       'menuitemradio',
       'option',
       'radio',
+      'separator',
       'slider',
       'switch',
-      'tab'
+      'tab',
+      'treeitem'
     ],
     // 5.4 button Element
     namingMethods: ['subtreeText']