add hint regarding RPs

Signed-off-by: Simon L <szaimen@e.mail.de>

php/templates/containers.twig

@@ -99,6 +99,7 @@
                                 If you have a dynamic IP-address, you can use e.g. <a href="https://ddclient.net/">DDclient</a> with a compatible domain provider for DNS updates.<br /><br/>
                                 If you only want to install AIO locally without exposing it to the public internet or if you cannot do so, feel free to follow <b><a href="">this documentation</a></b>.<br><br>
                                 If you should be using Cloudflare Proxy for your domain, make sure to disable the Proxy feature temporarily as it might block the domain validation attempts.<br /><br/>
+                                If you try to install AIO behind a Reverse Proxy (like Apache, Nginx and else), and you run into issues getting your domain accepted, see <b><a href="https://github.com/nextcloud/all-in-one/blob/main/reverse-proxy.md#6-how-to-debug-things">this documentation</a></b> for how to debug things. <br /><br/>
                                 <b>Hint:</b> If the domain validation fails but you are completely sure that you've configured everything correctly, you may skip the domain validation by following <a href="https://github.com/nextcloud/all-in-one#how-to-skip-the-domain-validation">this documentation</a>.
                             </details><br /><br />
                         {% endif %}