When processing custom emoji, ensure a non-animated version exists (#5230)

Use the non-animated version in web UI, but return both in API

app/serializers/rest/custom_emoji_serializer.rb

@@ -3,9 +3,13 @@
 class REST::CustomEmojiSerializer < ActiveModel::Serializer
   include RoutingHelper
 
-  attributes :shortcode, :url
+  attributes :shortcode, :url, :static_url
 
   def url
     full_asset_url(object.image.url)
   end
+
+  def static_url
+    full_asset_url(object.image.url(:static))
+  end
 end