Add ability to play sounds and send particles via the API #317
Description
As the title say, I suggest to add ways to play sounds and to send particles to a player using the API. In my case I want to write a note block music plugin. Why can't I write my plugin at the server level ? Because I want the music the keep playing when the player changes server. Anyway, these functionalities could be also useful for a lot of other applications until then impossible at the proxy level.
Sending sounds or particles almost always requires a position as parameter. And this position is often relative the player position. So I also suggest to add a way to get the player position. This position would be deduced by Velocity by tracking position packets. I don't know how heavy it would be to track these packets so if it's a potentially heavy task it could be interesting to make it optional and controlled by a config file or by plugins using the API, or both.