Add Tree Shaking Support
The current [`src/index.ts`](https://github.com/phosphor-icons/react/blob/master/src/index.ts) file is not optimized for tree shaking.

This results in unnecessary bundle size (~9MB) increases because unused icons are not properly eliminated by bundlers like Webpack or Rollup.

See generate **Lighthouse Treemap**:
![Image](https://github.com/user-attachments/assets/6a24de4f-dde1-4265-8b63-e9f07334a48e)

(*Created from a tiny project served by Vite Dev Server*)

Can change the exports like this to make it Tree-shaking compatible?

```ts
export { Acorn } from "./csr/Acorn";

// Instead
// export * from "./csr/Acorn";
// ...
```
