Add snapshot testing tool

[lemonmade]

Some similar ideas to vitest, probably also powered by Vite:

// MyComponent.tsx

export function MyComponent() {
  // ...
}

// in-file snapshots
if (import.meta.env.snapshot) {
  const {snapshot: defaultSnapshot} = await import('@lemonmade/react-snapshots');

  // Like my testing library
  const snapshot = defaultSnapshot.extend({
    render: (element) => <AdditionalContext>{element}</AdditionalContext>,
  });

  snapshot('default', () => <MyComponent />);
}

// ===
// MyComponent.snapshots.tsx

import {snapshot} from '@lemonmade/react-snapshots';
import {MyComponent} from './MyComponent.tsx';

snapshot('primary', () => <MyComponent primary />);
snapshot('subdued', () => <MyComponent subdued />);