Update ImageSliderType.php

Add param 'with_seconds' as stated in DateTimeType.

We need to force the browser to display the seconds by adding the HTML attribute step if not already defined.
Otherwise the browser will not display and so not send the seconds therefore the value will always be considered as invalid.

src/Form/ImageSliderType.php

@@ -134,13 +134,15 @@ public function buildForm(FormBuilderInterface $builder, array $options): void
                 'widget' => 'single_text',
                 'html5' => true,
                 'input' => 'datetime',
+                'with_seconds' => true
             ])
             ->add('display_to', DateTimeType::class, [
                 'label' => $this->trans('Display to', TranslationDomains::TRANSLATION_DOMAIN_ADMIN),
                 'required' => true,
                 'widget' => 'single_text',
                 'html5' => true,
                 'input' => 'datetime',
+                'with_seconds' => true
             ]);
 
         if ($this->isMultistoreUsed) {