- Add ResamplingSpCVDisc

[pat-s]

fixes #114

cc @alexanderbrenning

Adds

• ResamplingSpCVDisc
• ResamplingRepeatedSpCVDisc
• autoplot.ResamplingSpCVDisc
• autoplot.ResamplingRepeatedSpCVDisc

and also the respective plot() generics.

library(mlr3)
library(mlr3spatiotempcv)

task <- tsk("ecuador")
rsp <- rsmp("repeated_spcv_disc",
  folds = 4, radius = 200, buffer = 200,
  repeats = 2
)
rsp$instantiate(task)

autoplot(rsp, task, 1, crs = 4326, show_omitted = TRUE)

^{Created on 2021-04-11 by the reprex package (v1.0.0)}