Add legal, privacy, contact and roadmap pages

website/src/contact/index.njk

@@ -27,7 +27,7 @@ description: Contact options for KST4Contest.
     <article class="card">
       <h3>Email</h3>
       <p>For legal or website-related contact.</p>
-      <a href="mailto:TODO@example.com">TODO@example.com</a>
+      <a href="https://groups.google.com/g/kst4contest">Join the mailing list →</a>
     </article>
   </div>
 </section>