add 'dhtool'

- signed-off-by: trimstray <trimstray@gmail.com>

README.md

@@ -351,6 +351,7 @@ Only main chapters:
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://uselesscsp.com/"><b>Useless CSP</b></a> - public list about CSP in some big players (might make them care a bit more).<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://whynohttps.com/"><b>Why No HTTPS?</b></a> - list of the world's top 100 websites by Alexa rank not automatically redirecting insecure requests.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://cipherli.st/"><b>cipherli.st</b></a> - strong ciphers for Apache, Nginx, Lighttpd and more.<br>
+&nbsp;&nbsp;:small_orange_diamond: <a href="https://2ton.com.au/dhtool/"><b>dhtool</b></a> - public Diffie-Hellman parameter service/tool.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://badssl.com/"><b>badssl.com</b></a> - memorable site for testing clients against bad SSL configs.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://tlsfun.de/"><b>tlsfun.de</b></a> - registered for various tests regarding the TLS/SSL protocol.<br>
 &nbsp;&nbsp;:small_orange_diamond: <a href="https://sslmate.com/caa/"><b>CAA Record Helper</b></a> - generate a CAA policy.<br>