add is_following field on user endpoint

app/views/users/_user.json.jbuilder

@@ -3,5 +3,6 @@ json.joined_at user.created_at.strftime("%B %d, %Y")
 json.following_count user.following.count
 json.follower_count user.followers.count
 json.posts_count user.posts.count
+json.is_following user.is_following?(@current_user)
 
 json.url user_url(user, format: :json)