Add /privacy route

I don't link to this in the footer or anything yet, but TNT asked for
it as part of the NeoPass setup, so I currently just redirect to the
outdated Impress 2020 privacy policy. (It's outdated in the sense that
we share *less* data with our third party services now, e.g. we moved
our analytics and error tracking onto our own machines!)

config/routes.rb

@@ -88,6 +88,8 @@ OpenneoImpressItems::Application.routes.draw do
 
   # About pages!
   get '/terms', to: "about#terms", as: :terms
+  get '/privacy',
+    to: redirect(Rails.configuration.impress_2020_origin + "/privacy")
   get '/about/neopass', to: 'about#neopass'
 
   # Other useful lil things!