Add style for focus in modebar

Author: davidangarita1

src/components/modebar/modebar.js

@@ -44,7 +44,6 @@ proto.update = function(graphInfo, buttons) {
 
     this.element.setAttribute('id', modeBarId);
     this.element.setAttribute('role', 'toolbar');
-    this.element.setAttribute('tabindex', '0');
 
     this._uid = modeBarId;
     this.element.className = 'modebar modebar--custom';

src/css/_modebar.scss

@@ -17,6 +17,10 @@
     opacity: 1;
 }
 
+&:focus-within .modebar--hover .modebar-group {
+  opacity: 1;
+}
+
 .modebar-group {
     float: left;
     display: inline-block;