[DOCS] License text.

Author: szabosteve

docs/index-custom-title-page.html

@@ -176,4 +176,5 @@ <h4 class="mt-3">
     </div>
   </div>
 
-  <p class="my-4"><a href="https://www.elastic.co/guide/index.html">View all Elastic docs</a></p>
+  <p class="my-4"><a href="https://www.elastic.co/guide/index.html">View all Elastic docs</a></p>
+  <p class="my-4">The PHP logo available <a href="https://www.elastic.co/guide/index.html">here</a> is released under the Creative Commons <a href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> Attribution-Share Alike 4.0 International license</a>.</p>