[FR] Better legends for :vline and :hline

[kosukesando]

Using markershape = :vline or :hline for a scatter plot, the legend is too thin to recognize the color. Increasing the markerstrokewidth to increase visibility is an option, but then the lines in the plot itself blob up into one giant rectangle at that point. I could circumvent this in for example matplotlib by creating a custom legend, but AFAIK that is not an option for Plots.jl.

Is it possible for :vline and :hline to have its own custom legend so that it's not just a Shape([(0,1),(0,-1)]) but perhaps a rectangle?