Notification plugin for NATS

### What would you like to be added? I whould like to have a notification plugin that works with NATS (https://nats.io/). I already wrote it as you can see here: https://github.com/andreabravetti/crowdsec/tree/feature/notification-nats-plugin I would love to contribute if there is interest, let me know. ### Why is this needed? Because if you use NATS having a dedicated plugin for it is convenient and clean.