added translations

frontend/templates/_datepicker_scripts.html.twig

@@ -1,3 +1,4 @@
 {# Must load before the page's own init script — VindnDates.bindInputs() looks for window.flatpickr at call time. #}
 <script src="https://cdnjs.cloudflare.com/ajax/libs/flatpickr/4.6.13/flatpickr.min.js"></script>
-<script src="https://cdnjs.cloudflare.com/ajax/libs/flatpickr/4.6.13/l10n/de.js"></script>
+{# Calendar names/first weekday for the page language; English is built in. #}
+{% if app.request.locale != 'en' %}<script src="https://cdnjs.cloudflare.com/ajax/libs/flatpickr/4.6.13/l10n/{{ app.request.locale }}.js"></script>{% endif %}