Update index.md for better clarity and relationship between packages #3013

Job	Run time
lint	59s
docs (./packages/autogen-core)	1m 32s
format	57s
mypy (./packages/autogen-core)	2m 14s
mypy (./packages/autogen-magentic-one)	1m 9s
pyright (./packages/autogen-core)	56s
mypy (./packages/agbench)	58s
pyright (./packages/autogen-magentic-one)	56s
mypy (./packages/autogen-ext)	1m 47s
pyright (./packages/agbench)	49s
mypy (./packages/autogen-agentchat)	1m 8s
pyright (./packages/autogen-ext)	58s
pyright (./packages/autogen-agentchat)	49s
check-proto-changes-python	1m 17s
codecov (./packages/autogen-core)	59s
docs-example-check (./packages/autogen-core)	2m 27s
codecov (./packages/autogen-magentic-one)	1m 55s
markdown-code-lint	2m 6s
codecov (./packages/autogen-ext)	2m 54s
codecov (./packages/autogen-agentchat)	1m 2s
test (./packages/autogen-core)	1m 2s
test (./packages/autogen-magentic-one)	1m 26s
test (./packages/autogen-ext)	2m 42s
test (./packages/autogen-agentchat)	1m 6s
	34m 8s

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