doc: add whatsnew entry for current plotting

doc/source/pre/whatsnew/1.3.rst

@@ -151,3 +151,10 @@ provided site, but of it's image in the fundamental domain.
 
 This change is documented here for completeness.  We expect that the vast
 majority of users of Kwant will not be affected by it.
+
+Plotting currents with plotter.current
+--------------------------------------
+Quantities defined on system hoppings (e.g. currents calculated using
+`~kwant.operator.current`) can be directly plotted as a streamplot over the
+system using `kwant.plotter.current`. This is similar to how
+`kwant.plotter.map` can be used to plot quantities defined on sites.