Fixed custom NLog Target link on the homepage

Author: snakefoot

index.html

@@ -142,7 +142,7 @@ <h4> <i class="fa fa-file-o fa-fw"></i>
 
             The full list of targets is available on the <a href="{{ site.baseurl }}/config/?tab=targets">config options page</a>.
             If you didn't find the target to fit your needs, you can
-            <a href="https://github.com/nlog/NLog/wiki/How-to-write-a-Target">easily write a custom one</a>.
+            <a href="https://github.com/NLog/NLog/wiki/Extending-NLog">easily extend NLog with a custom target</a>.
 
 
         </p>