`stat_ecdf` add `pad` argument

[dhimmel]

I noticed ggplot2 has a pad argument for stat_ecdf:

If TRUE, pad the ecdf with additional points (-Inf, 0) and (Inf, 1)

But plotnine does not.

I am plotting some empirical cumulative distribution functions where the first value already contains over 50% of all observations. Having the step lines start at zero would be nice visually.