Make it clear that certain constructors require a redis connection.

[charleslee94]

Looking through issues, I see that several others including myself have had issues when deploying apps using bullmq and redis to dockerized containers.

A lot of the time, for classes like QueueEvents or FlowProducer not passing in an explicit redis connection will result in a default connection being passed, usually localhost.

Its not clear that these constructors require redis connections. It would be helpful if the examples in the docs provided clearer indications that you should pass in redis connections to these classes.

const connection = new Redis()
const events = new QueueEvents('Paint', connection)