localize flatpickr date format

Flatpickr can format date. Use a localized dateFormat.

app/assets/javascripts/admin/util.js.erb

@@ -25,7 +25,7 @@ $(document).ready(function(){
     }
   );
   window.FLATPICKR_DATE_DEFAULT = {
-    dateFormat: "Y-m-d H:i",
+    dateFormat: Spree.translations.flatpickr_date_format,
     locale: I18n.locale
   }
   window.FLATPICKR_DATETIME_DEFAULT = Object.assign(

app/views/spree/admin/shared/_translations.html.erb

@@ -3,6 +3,9 @@
   { :date_picker    => Spree.t(:js_format,
                               :scope => 'date_picker',
                               :default => 'yy/mm/dd'),
+    :flatpickr_date_format    => Spree.t(:flatpickr_date_format,
+                              :scope => 'date_picker',
+                              :default => 'Y-m-d H:i'),
     :abbr_day_names           => I18n.t(:abbr_day_names, :scope => :date),
     :add                      => I18n.t(:add, scope: :actions),
     :are_you_sure_delete      => Spree.t(:are_you_sure_delete),

config/locales/en.yml

@@ -3595,6 +3595,7 @@ See the %{link} to find out more about %{sitename}'s features and to start using
     date_picker:
       format: ! '%Y-%m-%d'
       js_format: 'yy-mm-dd'
+      flatpickr_date_format: "Y-m-d H:i"
     orders:
       error_flash_for_unavailable_items: "An item in your cart has become unavailable. Please update the selected quantities."
       edit: