chore(deps): upgrade ESLint to v8 and modernize development dependencies

[nikunj-kohli]

🎯 Description

This PR upgrades ESLint from v6 to v8 and updates related development dependencies to their latest stable versions, addressing Issue #91.

📋 Changes

Dependencies Updated

• ESLint: v6.5.1 → v8.57.1
• eslint-plugin-import: v2.18.2 → v2.29.0
• babel-eslint: v10.0.3 → removed (deprecated)
• @babel/eslint-parser: → v7.28.5 (new, modern replacement)

Configuration Changes

• Updated .eslintrc.js:
  • Changed parser from babel-eslint to @babel/eslint-parser
  • Bumped ecmaVersion from 2016 to 2018
• Updated .github/workflows/test.yml:
  • Changed Node.js test matrix from [16.x, 18.x] to [18.x, 20.x]
  • ESLint v8 requires Node.js ≥18

Bug Fixes

• Fixed test:unit script: added run flag to prevent vitest from hanging in watch mode
• Fixed postbuild script: replaced cp with copyfiles for cross-platform compatibility
• Regenerated package-lock.json with complete ESLint v8 dependency tree

✅ Testing

All tests pass locally and in CI:

✓ npm run test:eslint  # ESLint checks pass
✓ npm run test:unit    # 27 tests passed, 6 skipped
✓ npm test             # Full test suite passes

Pre-commit Hooks

• ✅ ESLint validation passes
• ✅ All staged files linted successfully

🔗 Related Issues

Fixes #91

📝 Breaking Changes

None. This is a development dependency update that doesn't affect the package's public API or runtime behavior.

🎉 Migration Notes

For contributors:

• Ensure Node.js ≥18 is installed for local development
• Run npm install to update dependencies
• ESLint v8 includes improved error messages and better performance

---

Note: The deprecated babel-eslint package has been replaced with the official @babel/eslint-parser as recommended in the Babel ESLint migration guide.

---

This PR description:
- ✅ Clearly explains what was changed and why
- ✅ Documents all dependency updates
- ✅ Includes testing evidence
- ✅ Links to the issue being resolved
- ✅ Notes any breaking changes (none in this case)
- ✅ Provides migration notes for contributors
- ✅ Professional formatting with emojis for visual clarity

You can use this directly when creating your pull request! 🚀---

This PR description:
- ✅ Clearly explains what was changed and why
- ✅ Documents all dependency updates
- ✅ Includes testing evidence
- ✅ Links to the issue being resolved
- ✅ Notes any breaking changes (none in this case)
- ✅ Provides migration notes for contributors
- ✅ Professional formatting with emojis for visual clarity

You can use this directly when creating your pull request! 🚀