Maps each chart type to the class that models it and the setup_* that
builds one. Read at run time by read_chart_config(), and at generation time
by data-raw/generate_schemas.R, so the two cannot disagree about which
chart types exist.
Examples
names(chart_registry())#> [1] "scatter3d" "timeseries" "survival" "calibration" "roc"
#> [6] "scatter" "confusion" "significance" "bar" "density"
#> [11] "histogram" "line" "pie" "boxplot" "sankey"
#> [16] "gantt" "network" "choropleth" "heatmap" "spectrogram"
#> [21] "a3"