fix(FEC-7591): player shell is not part of the tabbing traversal (#157)

adding the shell to the tabbing traversal, changing it tabIndex attribute to 0.

src/components/shell/shell.js

@@ -200,7 +200,7 @@ class Shell extends BaseComponent {
 
     return (
       <div
-        tabIndex="-1"
+        tabIndex="0"
         className={playerClasses}
         onClick={() => this.onClick()}
         onMouseOver={() => this.onMouseOver()}