Expose natlink onChangeCallback in aenea server

[mzizzi]

This is a feature request.

natlink provides callbacks for various state changes. We could proxy these events off to the server and do useful things with them like this: https://github.com/mzizzi/aenea-indicator

This feature would slightly get away from the pure "remote input" spirit of Aenea so I'm not sure how others would feel about exposing it.

Thoughts?

[calmofthestorm]

This seems useful, but what changes do you need to aenea for this? The linked repository seems to do this well as a grammar and a server plugin.