Add Mastodon service page

config/routes.rb

@@ -29,6 +29,8 @@ Rails.application.routes.draw do
         get 'qr_lnurlp'
       end
     end
+
+    resource :mastodon, only: [:show], controller: 'mastodon'
   end
 
   resources :settings, param: 'section', only: ['index', 'show', 'update'] do