Implement OpenAI Swarm example with groupchat

[yiranwu0]

Use groupchat's custom function to implement the openai swarm.

Why are these changes needed?

Related issue number

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• I've included any doc changes needed for https://autogenhub.github.io/autogen/. See https://autogenhub.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
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[yiranwu0]

Initial Commit. Todo: Organize code, draw stateflow figure and improve doc.

[sonichi]

Thanks. Could you add metadata to make it renderable on the website and searchable via tags?
After this PR is merged, in the next iteration, can we add some built-in speaker selection method so that users can directly import from the library to achieve the swarm-style orchestration?

[yiranwu0]

Thanks. Could you add metadata to make it renderable on the website and searchable via tags? After this PR is merged, in the next iteration, can we add some built-in speaker selection method so that users can directly import from the library to achieve the swarm-style orchestration?

I added the tags to be compiled on the website.
Yes, I will make another PR to implement this feature!