ISTWCMS-6611: adding template for views view unformatted, which adds index to variables

templates/views/views-view-unformatted.html.twig

+{#
+/**
+ * @file
+ * Default theme implementation to display a view of unformatted rows.
+ *
+ * Available variables:
+ * - title: The title of this group of rows. May be empty.
+ * - rows: A list of the view's row items.
+ *   - attributes: The row's HTML attributes.
+ *   - content: The row's content.
+ * - view: The view object.
+ * - default_row_class: A flag indicating whether default classes should be
+ *   used on rows.
+ *
+ * @see template_preprocess_views_view_unformatted()
+ *
+ * @ingroup themeable
+ */
+#}
+{% if title %}
+  <h3>{{ title }}</h3>
+{% endif %}
+{% for row in rows %}
+  {%
+    set row_classes = [
+    default_row_class ? 'views-row',
+  ]
+  %}
+
+  {% set row = row|merge({
+    content: row.content|merge({
+      '#uw_index': loop.index
+    })
+  })
+  %}
+
+  <div{{ row.attributes.addClass(row_classes) }}>
+    {{- row.content -}}
+  </div>
+{% endfor %}