Feature request

Feature description:
Two config options called something like message-on-vanish and message-on-unvanish which are broadcasted when vanish is turned on and off respectively

How the feature is useful:
This can be used to make fake join and quit messages. A similar feature was requested earlier (#2713) but was closed because there wasn't a reliable way to get join messages. This should fix that issue by allowing the server owners to input the format themselves.

#3881 does this work until now? Cause I open the jar files and add some this
Adds the config option below:

When a player enters/exits vanish, should a fake login/logout message be sent?

send-vanish-broadcast: false
The message is taken from messages.properties which defaults to the same as vanilla:

unvanishBroadcast=\u00a7e{0} joined the game
vanishBroadcast=\u00a7e{0} left the game

I don't know why this should be a config option, especially Strings. It should be a simple boolean to fake a join/quit message based on what's already in the config. Otherwise good idea.