feat: expose ESM build with debug (#1585)

So that debug logs can be printed with vite:

```js
import { defineConfig } from 'vite'
import react from '@vitejs/plugin-react'

export default defineConfig({
  plugins: [react()],
  server: {
    port: 4000
  },
  resolve: {
    conditions: ["development"]
  }
})
```

Reference: https://v2.vitejs.dev/config/#resolve-conditions

Related:

- https://github.com/socketio/socket.io/issues/4731
- https://github.com/socketio/socket.io/issues/4635
- https://github.com/socketio/socket.io-client/issues/1516