Allow articles to be sorted by "created" date.

Adding a new sort option to the `TeamType.articles` field: "created" date.

Reference: CV2-5851.

app/graph/types/team_type.rb

@@ -328,7 +328,7 @@ def tipline_requests(from_timestamp:, to_timestamp:)
 
   def articles(**args)
     sort = args[:sort].to_s
-    order = [:title, :language, :updated_at, :id].include?(sort.downcase.to_sym) ? sort.downcase.to_sym : :title
+    order = [:title, :language, :updated_at, :created_at, :id].include?(sort.downcase.to_sym) ? sort.downcase.to_sym : :title
     order_type = args[:sort_type].to_s.downcase.to_sym == :desc ? :desc : :asc
     articles = Explainer.none
     if args[:article_type] == 'explainer'