Add the `rightIcon` property to the JSON

[jesalynrose]

Update the MenuBuilderUtils Client Script Include to include the rightIcon property. I'm not entirely sure what will need to be changed, but you want to make sure if you're starting from a saved menu that the page can still import the JSON correctly when the component adds this property.

Likely need to:

• Add rightIcon property to the TreeNode in constructor and setter function
• Update the traverseJSON function