Box-and-whisker series. One box per category.
Fields:
:categories— list of category labels (one per box):stats— list of maps, one per box, each with%{min, q1, median, q3, max, outliers}keys.outliersis a (possibly-empty) list of y-values rendered as open markers beyond the whiskers.:hatch— IQR box fill (default cycles):label— legend label:stroke_width,:box_width(fraction of slot; default 0.6)