add voting category name to shrimpo serializer

app/serializers/shrimpo_vote_serializer.rb

@@ -1,6 +1,10 @@
 class ShrimpoVoteSerializer < ActiveModel::Serializer
-  attributes :score
+  attributes :score, :voting_category_name
   belongs_to :user
   belongs_to :shrimpo_entry
   belongs_to :shrimpo_voting_category
+
+  def voting_category_name
+    object.shrimpo_voting_category.name
+  end
 end