Separate documentation on nested chats

[jackgerrits]

What is the doc issue?

We should provide guidance beyond the migration document about how to handle nested chats.

https://microsoft.github.io/autogen/stable/user-guide/agentchat-user-guide/migration-guide.html#nested-chat

Link to the doc page, if applicable

New doc

[Vidit-Ostwal]

@jackgerrits
this might not be the best place to ask this.

Is there any kind of courses available for learning autogen?

[jackgerrits]

Please see the website for tutorial content produced by us and the community: https://microsoft.github.io/autogen/stable/user-guide/agentchat-user-guide/tutorial/index.html