It is important to understand that GitHub is not a platform for CV search or a job board. It's kind of a social network for developers.
You won't know if your candidate knows Node.Js, React, etc. GitHub will give you information about the activity of your candidate on the site (and, therefore, show whether the candidate is interested in his profession or not), will allow you to see code examples, figure out the popularity of a specialist (based on the number of followers).
In addition, GitHub can help you find links to your web developer's social networks.