This example renders a smiling face entirely with SVG primitives. It displays a yellow circular head with black stroke, two elliptical eyes, a curved mouth created with `d3.arc`, and two brow arcs. Built with React and d3.v5, it uses React’s declarative elements for circles and ellipses, while the mouth and brows are generated as path strings from `d3.arc` with specified angles and radii. The graphic is centered and drawn within an `<svg>` element.