Fork of Smiley Face Part IV
This example shows a yellow smiley face with black-outlined eyes and a mouth, centered on a square SVG canvas. It uses D3’s `arc` generator to create the mouth as a curved path, while React components render the background circle and eyes. The face is drawn using SVG primitives like `circle` and `path`, with all coordinates and dimensions defined as constants. The code combines React 16 and D3 v5, with the entire graphic composed from a single React component and rendered via `ReactDOM.render`.