Adding keep_empty argument to list_c, list_cbind, and list_rbind.

We have decided not to implement this feature for now since:

tidyr::unchop() solves the problem already in a very robust way https://github.com/tidyverse/purrr/issues/1096#issuecomment-2315466918
We can't seem to justify the argument for list_cbind(), suggesting something feels off with putting it here in purrr

@SokolovAnatoliy we apologize about that! We hope you had fun at TDD anyways, and it seems like you got to do some other PRs in other repos, which is awesome! Thanks again!

tidyverse / purrr

Adding keep_empty argument to list_c, list_cbind, and list_rbind. #1144