docs: add cryptle hack challenge url

Signed-off-by: Nick Vidal <[email protected]>

Author: Nick Vidal

client/index.html

@@ -45,7 +45,7 @@ <h3>Multi Player (MP)</h3>
         <h3>Hack Challenge</h3>
         <p><strong>Guess the words by <em>hacking</em> the server as root:</strong></p>
         <p>&#128274; Cryptle encrypts data in use: not even the OS has access to it.</p>
-        <p>&#x1F469;&#x200D;&#x1F4BB; <a href="#">Submit</a> an open source application to run with root privileges.</p>
+        <p>&#x1F469;&#x200D;&#x1F4BB; <a href="http://enarx.dev/cryptle">Submit</a> an open source application to run with root privileges.</p>
         <button title="Close" class="close_modal_help">✖</button>
       </div>
     </div>