This example demonstrates how to draw a smiley face using React and D3. It renders a yellow circle with black stroke for the face, two black eyes, and a mouth created with the `d3.arc()` path generator. The SVG elements are positioned using a centered `<g>` transform, with eye and mouth coordinates computed from fixed offsets and radii. The code uses React 16.9, D3 v5, and renders to SVG.