js: add new options to permittedOperations

--

* reflecting the new optional strings accepted by the backend.
  'file_name' and 'sender' can be  used via the 'additional'
  parameter in encrypt operations

lang/js/src/permittedOperations.js

@@ -94,6 +94,12 @@ export const permittedOperations = {
             },
             'wrap': {
                 allowed: ['boolean']
+            },
+            'sender': {
+                allowed: ['string']
+            },
+            'file_name': {
+                allowed: ['string']
             }
         },
         answer: {