learn D3 and React
This example demonstrates a single yellow circle with a thick black stroke, centered within an SVG canvas. It shows how to create a basic React application that renders SVG graphics. The code uses React and ReactDOM to mount the component into the DOM, and defines the circle using standard SVG attributes like `cx`, `cy`, `r`, `fill`, and `stroke`. It is a minimal template for integrating D3-style visualization concepts with React's declarative component model, though it does not use any D3 libraries directly.