Support addition of sibling category

[shanavas786]

Magento supports addition of root category and subcategory. It would be nice to add sibling category addition too.

[magento-engcom-team]

@shanavas786 please refer to the Community Forums or the Magento Stack Exchange site for advice or general discussion about this issue. The GitHub issue tracker is intended for technical issues only.
Feel free to submit pull request for this issue 👍