docs: add Request Deduplication section and example to main README

[Kaustav5505g]

Description

Added a dedicated Request Deduplication section and copy-pasteable code example to the main README.md to make the feature easily discoverable.

Fixes #31

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation/Website update (changes to READMEs, examples, inline comments, or the documentation website)

Checklist

Design & Parity

• If this introduces a new configuration option or public API, I have implemented equivalent options/behavior in both TypeScript and Python packages.
• The core packages remain dependency-free (no new external runtime dependencies added).
• I have updated the relevant package-specific README.md or general documentation where necessary.
• If applicable, I have updated the examples or website to reflect these changes.

Quality & Testing

• I started the sandbox Express server (cd sandbox && npm install && npm start) in a separate terminal before running the tests.
• TypeScript Package: I have run the TypeScript tests (npm install && npm run build && npm test inside packages/smooth-api-ts) and all tests passed.
• Python Package: I have run the Python tests (pip install -e ".[dev]" && pytest inside packages/smooth-api-py) and all tests passed.
• I have added new tests to cover my changes.
• I have commented my code, particularly in hard-to-understand areas, and updated JSDoc/docstrings.

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[AryanSharma48]

LGTM, Thanks for the contribution @Kaustav5505g