ISTWCMS-6494: add a class to the block header to make it easier to identify

templates/blocks/block.html.twig

@@ -45,7 +45,7 @@
     {{ title_prefix }}
     {% if label %}
       {% if heading_level %}
-        <{{ heading_level }}{{ title_attributes }}>{{ label }}</{{ heading_level }}>
+        <{{ heading_level }}{{ title_attributes }} class="block-title">{{ label }}</{{ heading_level }}>
       {% else %}
         <h2{{ title_attributes }}>{{ label }}</h2>
       {% endif %}