Heatmap with a legend

enableLegend: true puts a color bar underneath the grid that maps the colors of the cells onto the values they stand for. The bar shows the same discrete color buckets that the grid uses, and legend.title and legend.tickFormat label it. The legend takes its height out of the configured one, so the visualization as a whole still measures 1000 × 600 pixels. Toggle legend rebuilds the heatmap with the legend off, which shows how much room it takes, and Export SVG downloads the heatmap as an SVG file with the same legend underneath it.