feat: updated configurations for the flat config format

[SergoDrovski]

Add ESLint 9 Support

🎯 Problem

This plugin currently doesn't work with ESLint 9 due to:

• Incompatible plugin structure
• Missing schema validation for rule options
• Deprecated context.report() usage
• Error: Value [{"trustedLibraries":["lib"]}] should NOT have more than 0 items

🚀 Solution

• ✅ Added ESLint 9 flat config support
• ✅ Updated plugin metadata structure
• ✅ Added proper schema validation for rule options
• ✅ Updated context.report() calls to object syntax
• ✅ Maintained backward compatibility with ESLint 8
• ✅ Added usage examples for both config formats

📋 Changes

Core Changes

• index.js: Updated plugin structure with metadata and flat config support
• rules/catch-potential-xss-react.js: Added schema validation and updated report calls
• rules/catch-potential-xss-vue.js: Added schema validation and updated report calls
• utils.js: Updated context.report() in defineTemplateBodyVisitor

Documentation

• Updated README with ESLint 9 usage examples
• Added flat config examples
• Documented migration steps

🧪 Testing

Tested with:

• ESLint 9.30.1 ✅
• ESLint 8.57.1 ✅ (backward compatibility)
• React projects ✅
• Vue projects ✅

Before

Error: Key "rules": Key "risxss/catch-potential-xss-react":
Value [{"trustedLibraries":["@frontend/core/shared/lib/cleanHTML/safeHTML"]}] should NOT have more than 0 items.

After

✅ No errors, rules work correctly with options

📦 Usage Examples

ESLint 9 (Flat Config)

import risxss from 'eslint-plugin-risxss';

export default [
  {
    plugins: { risxss },
    rules: {
      'risxss/catch-potential-xss-react': ['error', {
        trustedLibraries: ['@frontend/core/shared/lib/cleanHTML/safeHTML']
      }]
    }
  }
];

ESLint 8 (Legacy Config)

module.exports = {
  plugins: ['risxss'],
  rules: {
    'risxss/catch-potential-xss-react': ['error', {
      trustedLibraries: ['@frontend/core/shared/lib/cleanHTML/safeHTML']
    }]
  }
};

🔄 Migration Guide

For users upgrading to ESLint 9:

1. Update to flat config format
2. Change plugin import syntax
3. Update rule configuration (no breaking changes in options)

⚠️ Breaking Changes

None - full backward compatibility maintained.

📝 Checklist

• Code follows project style
• Backward compatibility maintained
• Documentation updated
• Manual testing completed
• No breaking changes introduced

---

This PR resolves the ESLint 9 compatibility issues while maintaining full backward compatibility with ESLint 8.