Add checksums to index

Adds checksums to index file

roles/netbootxyz/templates/index.html.j2

@@ -64,6 +64,10 @@ chain --autofree http://{{ boot_domain }}/menu.ipxe || echo HTTP failed, localbo
     </tr>
     {% endfor %}
   </table>
+
+  <p>Checksums<p>
+
+  <a href="ipxe/{{ site_name }}-sha256-checksums.txt">SHA256 checksums</a>
   </div>
   </body>
 </html>