replacements: link to old and new media assets.

On the /post_events and /post_replacements pages, include links to the old and new media assets
pages so you can compare the two images.

app/controllers/post_events_controller.rb

@@ -9,7 +9,7 @@ class PostEventsController < ApplicationController
     end
 
     @post_events = authorize PostEvent.paginated_search(params, defaults: { post_id: @post&.id }, count_pages: @post.present?)
-    @post_events = @post_events.includes(:creator, :post, model: [:post]) if request.format.html?
+    @post_events = @post_events.includes(:creator, :post, model: [:post, :media_asset, :old_media_asset]) if request.format.html?
 
     respond_with(@post_events)
   end