Document how to add a new trigger

[peterclemenko]

I want to add two new triggers, one of mqtt, one for redis pubsub, how would I add these

(This might lead to rabbitmq and kafka and nats as well)

[frikky]

In short before we add this properly:

New triggers are both frontend and backend configurations. The problem with making new ones is that they often require background processing to be done. That's why our recommendation is to:

• Set up a service yourself that listens to the Queue systems
• Make the service forward the data as a post request
• Set up a webhook in Shuffle that can receive the data

MQ systems won't be any better implemented otherwise.