Adding groups to the Contextual Menu

[GomezIvann]

Checklist

• The Build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

Description
In the previous weeks, we have been working on a new component, the DxcContextualMenu. During its development, a new need arose: adding groups to the component, which can contain single elements or other groups.

To implement this new functionality we had to use a recursive algorithm to optimize the rendering of nested components up to N level. This had a few consequences for the component API:

• defaultSelectedItemIndex has been removed. The default selection employing an index became more complex with the inclusion of groups.
• No more icons in the slot position. Now you can only place a badge on the right side of an item.
• The component no longer exports a Badge. The user should use the regular DxcBadge as the value of the prop with the same name.

The design can be checked here.

[kukoc]

Just a couple of minor things that I believe should be changed