Color and Size Legends
This example demonstrates how to create separate legends for ordinal color scales and quantitative size scales using D3 v5. A color legend maps fruit names to distinct colors with equally spaced circles, while a size legend displays circular markers whose radii scale proportionally to numeric values using `scaleSqrt`. Both legends are implemented as reusable functions via `selection.call()`, with the color legend using `scaleOrdinal` and the size legend using `scaleSqrt().ticks()` to generate tick values. The SVG rendering includes custom text and circle styling defined in external CSS.