[REF] support select2 for countryFilter

src/FilterType/CountryFilterType.php

@@ -13,7 +13,7 @@ public function buildForm($builder, array $options = [], $data = null): void
                 'required'           => false,
                 'translation_domain' => 'unlooped_grid',
                 'attr'               => [
-                    'class' => 'custom-select',
+                    'class' => ($options['use_select2'] ? 'initSelect2' : 'custom-select'),
                 ],
                 'preferred_choices' => $options['preferred_choices'],
             ])