Add note on consumer dispatch for server events

[shopwhizzy]

Added note about dispatching the consumer for server events.

Description (*)

Story

Bug

Task

Fixed Issues (if relevant)

1. magento-commerce/facebook-for-magento2#<issue_number>: Issue title

Manual testing scenarios (*)

1. ...
2. ...

Questions or comments

Checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)