Update ReadMe of this sample example

Can someone add a detailed ReadMe on the scope of this sample repo/ example. It is difficult to follow w/o a README.

Look at the repository's existing structure and the sample examples to understand the scope of the A2A Protocol. Review other sample READMEs in the repo for style. Write a README.md file explaining the purpose, setup, and usage of this sample. Ensure it helps newcomers follow the example.

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