add class selector dynamically to product search form

templates/bootstrap/forms/product_search.html

@@ -1,4 +1,10 @@
 {% load static %}
 {% load crispy_forms_field %}
 
-{%  if input.name == "search" %}<button class="left-menu__search-btn"><img src="{% static "img/search.svg"%}" alt="Поиск"></button>{% else %}{{ field }}{% endif %}
+{% spaceless %}
+    {% if input.name == "search" %}
+        <button class="{{ input.field_classes }}"><img src="{% static "img/search.svg" %}" alt="Поиск"></button>
+    {% else %}
+        {{ field }}
+    {% endif %}
+{% endspaceless %}