Add documentation about how to send an event to pub/sub

[thclark]

Feature request

About me

If you're new to the twined ecosystem, and you don't mind, it'd be great to hear a little bit of the wider context about
you and what you're working on, so we can understand how best to help.

Use Case

Please [describe your motivation and use case].

Current state

Please describe what you're doing presently to work around this or achieve what you're doing.