Enhance README with subpath support details

[cosmo-ray]

Added support for subpath in JSON path queries.

📦 Pull Request Template

Description

Please include a summary of the changes and the related context. If this is a feature, explain the motivation. If it's a bug fix, describe what was broken.

Fixes: # (if applicable)

Type of Change

Please check the relevant option(s):

• 🐛 Bug fix
• ✨ New feature
• 🧹 Code cleanup or refactor
• 📝 Documentation update
• 🔧 Build or CI-related change
• 🔒 Security fix
• Other (specify):

How Has This Been Tested?

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• Manual testing
• Unit tests
• Integration tests
• Not tested yet

Commands used (if applicable):

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my-cli-tool build --verbose
my-cli-tool test

Checklist

• I have followed the Contributing Guidelines
• I have added tests or explained why they are not needed
• I have updated relevant documentation (README, examples, etc.)
• My changes follow the Conventional Commits specification
• My commits include appropriate Gitmoji

Additional Context

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