Move the produced events details out of spec.md

[AlexandraRoatis]

Problem
The produced events listed below are no longer viewed as part of the specification. However, they can be useful for debugging. They should be relocated to another document.

• Trigger Events
• Broker Events
• Channel Events
• Subscription Events

Persona:
Which persona is this feature for?

• System Integrator
• Contributor

Exit Criteria

1. Remove the events sections from spec.md.
2. Create a new document where to include this information.
3. Set up some recommendations for adding new information to the document.

[AlexandraRoatis]

Fixed in #4594. The new file is helper.md.