Pie plot
A pie chart shows the distribution of stroke cases across BMI categories—Normal, Overweight, and Obese—as percentages of the total. The dataset is loaded via `d3.csv` from a GitHub gist, with BMI values filtered to stroke patients and grouped into the three categories. Using D3 v6, the chart is rendered as SVG paths generated by `d3.pie` and `d3.arc`, with a `d3.scaleOrdinal` color scheme. A legend, positioned via `d3.selectAll`, displays each category’s name and its computed percentage.