Resolve "Cloud WP: Cloud Services & Portfolio"

Closes #134 (closed)

services/cloud/Service_Portfolio.html

@@ -53,6 +53,12 @@ The provision of Helmholtz Cloud Services requires technical and organisational
     </div>
 </div>
 
+<p>
+            <a href="https://www.hifis.net/doc/service-portfolio/" type="button" class="btn btn-outline-secondary btn-sm">
+                <i class="fas fa-file-alt"></i> Documentation
+            </a>
+</p>
+
 <div class="image-attrib">Images by Katerina Limpitsouni via <a href="https://undraw.co/">undraw.co</a></div>
 
 <div>