Task 9 Area Chart
This area chart visualizes the evolution of funding in West Africa for 2020, using a stacked layout to display categories of earmarked, softly earmarked, tightly earmarked, and unearmarked contributions. It loads data from a CSV file containing diabetes statistics via `d3.csv`, then stacks the data with `d3.stack()`. The chart uses `d3.scalePoint` for the x-axis, `d3.scaleLinear` for the y-axis, and `d3.area` to generate the stacked paths. Tooltips implemented with mouseover and mouseleave events highlight individual areas, while the SVG rendering includes custom titles, labels, and a legend.