Update reference docs description

Author: const-cloudinary

docs/themes/cloudinary/index.twig

@@ -12,7 +12,11 @@
     <div class="page-header">
         <h1> {{ project.config('title') }}</h1>
     </div>
-
+    <div class="description">
+        <p>This reference provides details on all PHP SDK transformation namespaces and classes.</p>
+        <p>For details on the PHP SDK management namespaces and classes,
+            see the <a href="/documentation/sdks/php/">PHP SDK Management Reference.</a></p>
+    </div>
     {% if classes %}
         <h2>Classes</h2>
         {{ render_classes(classes) }}

docs/themes/cloudinary/layout/layout.twig

@@ -39,7 +39,7 @@
                     <!--li><a href="{{ path('traits.html') }}">Traits</a></li--CLD_MOD-->
                     <li><a href="{{ path('doc-index.html') }}">Index</a></li>
                     <li><a href="{{ path('search.html') }}">Search</a></li>
-                    <li><a href="/documentation/sdks/php/">PHP SDK Reference</a></li>
+                    <li><a href="/documentation/sdks/php/">PHP SDK Management Reference</a></li>
                     <li><a href="/documentation/php2_integration" target="_blank">SDK User Guide</a></li>
                 </ul>
             </div>