Add Nishanth Singaraju as author to Vision Cookbook (#2497)

AI Impact Summary

An author list in the Vision Cookbook repository has been augmented with a new maintainer entry for Nishanth Singaraju (nsingaraju-oai), including name, GitHub profile, and avatar. This fixes attribution and ensures future changes are associated with the correct contributor. The change is primarily governance/documentation metadata; downstream tooling that builds contributor lists or approves PRs will reflect the updated maintainer mapping. The snippet also shows a UI permission message ('You can’t perform that action at this time.'), which may indicate current user permissions constraints that could affect merging or updating contributor data.