selection.sort(compare)
Returns a new selection that contains a copy of each group in this selection sorted according to the compare function. After sorting, re-inserts elements to match the resulting order (per selection.order).
The compare function, which defaults to ascending, is passed two elements’ data a and b to compare. It should return either a negative, positive, or zero value. If negative, then a should be before b; if positive, then a should be after b; otherwise, a and b are con