Fix documentation links

Author: sagikazarmark

_data/navigation.yml

@@ -5,12 +5,12 @@
 
 - icon: puzzle-piece
   title: Plugins
-  url: https://github.com/php-http/plugins
+  url: http://docs.php-http.org/en/latest/plugins/index.html
   external: true
 
 - icon: book
   title: Documentation
-  url: http://docs.httplug.io
+  url: http://docs.php-http.org/en/latest/httplug/introduction.html
   external: true
 
 - icon: github

index.html

@@ -21,7 +21,7 @@ <h2>Decouple your package from implementation</h2>
                     without binding to a specific implementation.<br><br>
 
                     Read more about the why and how of the HTTP client abstraction
-                    <a href="http://docs.httplug.io" target="_blank">in our documentation</a>.
+                    <a href="http://docs.php-http.org/en/latest/httplug/introduction.html" target="_blank">in our documentation</a>.
                 </p>
             </div>
         </div>