Adding !players command for Discord

[LoneWolfHT]

This commented out code here is for receiving data from MT. https://github.com/MT-CTF/ctf-discord-bot/blob/057fe9381d71cfab8c4ac6352b8faca7a8a31c05/index.js#L250-L254

To send all you need is this then IIRC

if http then
    http.fetch({
        method = "PUT",
        url = "127.0.0.1:31337",
        data = "Player list requested by bot",
    }, function() end)
end

[moreavy]

I don't think we need /players command because we has the /status command in-game.