add nextcloud to nav

Signed-off-by: Arthur Lu <learthurgo@gmail.com>

index.html

@@ -21,6 +21,7 @@
 				<button onclick="window.location.href='https://wiki.tronnet.net';">Cluster Documentation</button>
 				<button onclick="window.location.href='https://mail.tronnet.net';">Tronnet Mail</button>
 				<button onclick="window.location.href='https://ldap.tronnet.net';">Cluster LDAP</button>
+				<button onclick="window.location.href='https://nextcloud.tronnet.net';">Cluster Nextcloud</button>
 			</div>
 		
 			<h3>User Directory</h3>