add age notice

signup/index.php

@@ -42,6 +42,7 @@ include __DIR__.'/../header.php';
             <p>
                 <em>signing up implies agreement with our <a href="/wiki/?page=code-of-conduct">code of conduct</a>. please give it a read.</em>
             </p>
+            <p>you must be at least 13 years or older to sign up and use tilde.team.</p>
 
             <button class="btn btn-primary" type="submit">submit</button>
 

wiki/pages/tos.md

@@ -15,6 +15,8 @@ its services fair for everyone. the following offences will result in a service
 tl;dr: don't do anything illegal or harmful, especially anything that could 
 [anger the hosting company](https://www.ovh.com/world/support/terms-and-conditions/)
 
+you must be at least 13 years or older to use tilde.team.
+
 here are some things that we don't allow:
 
 * deliberately defacing the accounts of other users