Support not showing `fill` variable as a column

[talegari]

Is it possible to not show the fill column, but fill by it.

The second example in the vignette adds carrier to the right end:

easyalluvial::alluvial_long(easyalluvial::quarterly_flights, key = qu, value = mean_arr_delay, fill = carrier, id = tailnum )

Instead, can carrier be shown as 'legend'?