add submitter timezone

app/javascript/submission_form/form.vue

@@ -1390,6 +1390,7 @@ export default {
 
         if (isLastStep && !emptyRequiredField && !this.inviteSubmitters.length && !this.optionalInviteSubmitters.length) {
           formData.append('completed', 'true')
+          formData.append('timezone', Intl.DateTimeFormat().resolvedOptions().timeZone)
         }
 
         let saveStepRequest

app/models/submitter.rb

@@ -16,6 +16,7 @@
 #  preferences   :text             not null
 #  sent_at       :datetime
 #  slug          :string           not null
+#  timezone      :string
 #  ua            :string
 #  uuid          :string           not null
 #  values        :text             not null