Added support for latest BungeeCord.

Please note that the latest BungeeCord changes introduced a packet encoding bug in features TAB offers that causes <1.13 players to be disconnected immediately on join. This bug is inherited by forks as well, including Waterfall and possibly further forks as well.
Considering the bungee update didn't add anything meaningful other than support for some 1.20.3 snapshot, it is better to stay on an older version of the proxy (BungeeCord #1759 or lower, Waterfall #548 or lower) until this is fixed in BungeeCord.
Disabling the plugin for <1.13 players to avoid the disconnect would be a bad solution for many reasons.