tools/snippets: add documentation and basic tests for placeholder sni…

[d-mahi14]

Fixes #9995

Summary

This PR replaces placeholder TODOs in tools/snippets with meaningful documentation and adds simple tests for the exported snippet function.

Changes

• lib/main.js: Implemented a minimal placeholder snippet function and updated JSDoc.
• lib/index.js: Updated module-level documentation and exports.
• test/test.js: Added basic tests verifying that the snippet function exists and returns input values unchanged.

Motivation

Improves the onboarding experience for new contributors by:

• Replacing TODOs with clear JSDoc
• Demonstrating how functions are documented and tested
• Providing minimal, functional tests

Testing

• Ran node test/test.js locally successfully
• Verified that the snippet function behaves as expected
• No changes to other modules

• Read, understood, and followed the contributing guidelines

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[kgryte]

@d-mahi14 Thank you for opening this PR; however, we won't be accepting the proposed changes. The entire point of the snippets is that they should be copied and the TODOs indicate what devs copying the snippets should do in order to ensure the snippet is tailored to the respective package. Meaning, the presence of TODO is intentional and not something we want to change.

Thanks again for your interest, and we look forward to your future contributions.