Add config option to create auto updating message with current queue members

[niklhut]

Should be possible to create with something like /config queue create_public_list. The message should auto update as soon as someone joins or leaves the queue as well as when a person is taken care of by a tutor.

This means the created message should always be up to date with the current queue status. Similar to a /admin queue list message, which does not auto update.

Additionally it should only be able to create one such message per guild.