DEV: enable cors to all cdn get requests from workbox. (#10685)

Now all external requests from the service worker will be in CORS mode without credentials.

app/controllers/theme_javascripts_controller.rb

@@ -13,6 +13,8 @@ class ThemeJavascriptsController < ApplicationController
 
   before_action :is_asset_path, :no_cookies, only: [:show]
 
+  cdn_action only: [:show]
+
   def show
     raise Discourse::NotFound unless last_modified.present?
     return render body: nil, status: 304 if not_modified?