Add PSR-20 link to the homepage

Author: Jean85

source/index.twig

@@ -62,6 +62,7 @@ $object = new ClassName();
                         <li><a class="home_features__link" href="/psr/psr-13/">PSR-13: Hypermedia Links</a></li>
                         <li><a class="home_features__link" href="/psr/psr-14/">PSR-14: Event Dispatcher</a></li>
                         <li><a class="home_features__link" href="/psr/psr-16/">PSR-16: Simple Cache</a></li>
+                        <li><a class="home_features__link" href="/psr/psr-20/">PSR-20: Clock</a></li>
                     </ul>
                 </div>
                 <div class="home_features__editor">