M2C-22619 Add JSDoc and description

Author: ptylek

lib/web/mage/tabs.js

@@ -135,6 +135,8 @@ define([
         },
 
         /**
+         * Checks if element is not in nested container to keep the correct scope of collapsible
+         * @param {Number} index
          * @param {HTMLElement} elem
          * @private
          * @return {Boolean}