test changes Gapminder Data in React and D3 - interactive regions
Gapminder country data from 1950 to 2015 is plotted as an interactive scatterplot, with a year slider when time is on the x-axis, and dropdowns to select different economic and demographic attributes. A world map background, rendered with `d3.geoNaturalEarth1` and `d3.geoPath`, colors countries by World Bank region, with click-to-select and hover highlighting that filters the plotted circles. Built with React and D3 v5, using `scaleLinear`, `scaleOrdinal`, and `scaleSqrt` for scales, and SVG elements for axes, legend, and marks.