[Docs] Improved Conversation Patterns documentation

[marklysze]

Why are these changes needed?

Improve and expand the documentation around conversation patterns.

Related issue number

Closes #975

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/docs/contributor-guide/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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