hue argument for xarray.plot.step() for plotting multiple histograms over shared bins

Is your feature request related to a problem? Please describe.

I love how efficiently we can plot line data for different observations using xr.DataArray.plot(hue={hue coordinate name}) over a 2D array, and I have appreciated xr.DataArray.plot.step() for plotting histogram data using interval coordinates. Today, I wanted to plot/compare several histograms over the same set of bins. I figured I could write xr.DataArray.plot.step(hue={...}), but I found out that this functionality is not implemented.

Describe the solution you'd like

I think we should have a hue kwarg for xr.DataArray.plot.step(). When specified, we would be able to plot 2D data in the same way as xr.DataArray.plot(), except that we get a set of step plots instead of a set of line plots.

Describe alternatives you've considered

• Use xr.DataArray.plot() instead. This is effective for histograms with many bins, but inaccurately represents histograms with coarse bins
• Manually call xr.DataArray.plot.hist() on each 1D subarray for each label on the hue coordinate, adding appropriate labels and legend. This is fine and my current solution, but I think it would be excellent to use the same shorthand that was developed for line plots.

Additional context

I didn't evaluate the other plotting functions implemented, but I suspect that others could appropriately consider a hue argument but do not yet support doing so.

Start at xr.DataArray.plot.step() and compare it with xr.DataArray.plot() on a 2D array using a hue coordinate. Trace the existing xr.DataArray.plot.hist() behavior and relevant plotting tests; done means shared-bin histograms render as separate labeled step plots for each hue slice.