Update using.rst (#9714)

Add a link to the third-party DNS authentication plugin using SOLIDserver

certbot/docs/using.rst

@@ -324,6 +324,7 @@ Infomaniak_        Y    N    DNS Authentication using Infomaniak Domains API
 dns-multi_         Y    N    DNS authentication of 100+ providers using go-acme/lego
 dns-dnsmanager_    Y    N    DNS Authentication for dnsmanager.io
 standalone-nfq_    Y    N    HTTP Authentication that works with any webserver (Linux only)
+dns-solidserver_   Y    N    DNS Authentication using SOLIDserver (EfficientIP)
 ================== ==== ==== ===============================================================
 
 .. _haproxy: https://github.com/greenhost/certbot-haproxy
@@ -349,6 +350,7 @@ standalone-nfq_    Y    N    HTTP Authentication that works with any webserver (
 .. _dns-multi: https://github.com/alexzorin/certbot-dns-multi
 .. _dns-dnsmanager: https://github.com/stayallive/certbot-dns-dnsmanager
 .. _standalone-nfq: https://github.com/alexzorin/certbot-standalone-nfq
+.. _dns-solidserver: https://gitlab.com/charlyhong/certbot-dns-solidserver
 
 If you're interested, you can also :ref:`write your own plugin <dev-plugin>`.