Create Your Own Manager Agent documentation page & use of @agent decorator

[andrewn3]

https://docs.crewai.com/how-to/custom-manager-agent

Would be good if this page is updated to show examples using the @agent decorator method, for custom agents - as the example shows that normal agents should be included in the crew agents definition and the manager should be excluded and also I think the manager needs to be defined so it can be referenced in the crew definition manager_agent=

Ideally i would want to define the manager in the same yaml file as the other agents - does this need a @manager_agent decorator defining ???