Add policy middleware to default Server stack

Author: snuggs

server/index.es

@@ -1,5 +1,5 @@
 const
-  { auth, cors, security, compressor, negotiator, librarian, mixins, assets }
+  { auth, cors, security, policy, compressor, negotiator, librarian, mixins, assets }
     = require ('middleware')
 
 
@@ -12,6 +12,7 @@ module.exports = class extends require ('koa') {
     stack = [
       cors        // why is this not a function...
     , security () // and this IS a function?
+    , policy ()   // and this IS a function?
     ].concat ( stack )
 
     for (let middleware of stack)