feat: add support for JS config files

[SargeKhan]

Summary

• Extends config loading to support both JSON and JS config files
• JSON files take priority over JS files
• Maintains backward compatibility with existing JSON configs

Priority order

1. {env}.{name}.config.json
2. {name}.config.json
3. {env}.{name}.config.js
4. {name}.config.js

Usage

JS config files should export an object with namespace keys:

module.exports = {
  namespace1: { /* config */ },
  namespace2: { /* config */ }
}