[Suggestion]Can't integrate with BungeeCord related plugins.

[Zen910]

I noticed that zMenu offers a action type:

• type: connect
  server:

which is good, because the /server command is a Bungee Proxy command, can not be exec by spigot server.

Worth noting that, not only /server command, there are potentially many Bungee Proxy commands that need to be encapsulated in a GUI menu.
Such as SkinsRestorer. As it runs under proxy mode, it provides a proxy command /skins to open the GUI menu for itself. However, the command cant be support by item.commands or item.consoleCommands.

Forgive me if I was wrong, the /skins command runs on the same mechanism as /server I guess. Really hopes to adjust code architecture to support "bungeeCommand".

[Zen910]

I also noticed in the Doc:

• type: shopkeeper
  name:

Such support for a specific plugin is good for simplifying the config work, but maybe trivial and less flexible. It can be implemented by the commands config.

There are many other plugins that could be integrated with zMenu, it seems impossible to offer types for each.

[Zen910]

As I found in src/main/java/fr/maxlego08/menu/requirement/actions/ConnectAction.java:

@Override
protected void execute(Player player, Button button, InventoryEngine inventory, Placeholders placeholders) {
    ByteArrayDataOutput out = ByteStreams.newDataOutput();
    out.writeUTF("Connect");
    out.writeUTF(server);
    player.sendPluginMessage(this.plugin, "BungeeCord", out.toByteArray());
}

Is the BungeeCord exposed api to exec the following:
ByteArrayDataOutput out = ByteStreams.newDataOutput();
out.writeUTF("Plugin");
out.writeUTF(command);
player.sendPluginMessage(this.plugin, "BungeeCord", out.toByteArray());

I have no experience in Minecraft-related development. I haven't found the protocol Doc about resolving the raw message being sent to Bungee, but it seems feasible.

Reference:
①org.bukkit.entity.Player.sendPluginMessage Doc: https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/plugin/messaging/PluginMessageRecipient.html#sendPluginMessage(org.bukkit.plugin.Plugin,java.lang.String,byte%5B%5D)

②BungeeCord api Doc:
https://ci.md-5.net/job/BungeeCord/ws/api/target/apidocs/net/md_5/bungee/api/plugin/Command.html