Add "all courses" menu item

apps/course/templates/course/inclusion/category_menu_items.html

@@ -1,5 +1,8 @@
 {% for cat in category_items %}
+<a class="header__link" href="{% url 'courses' %}">
+  <div class="header__title">Все курсы</div>
+</a>
 <a class="header__link{% if category.0 == cat.title %} active{% endif %}" data-category-name="{{ cat.title }}" href="{% url 'courses' %}?category={{ cat.title }}">
   <div class="header__title">{{ cat.title }}</div>
 </a>
-{% endfor %}
+{% endfor %}