Simple, experimental replacement for now. Tries to keep the previous key
functionality intact:
use <leader>e to open working directory in vifm, <leader>E to open the
directory of the current file.
Some problems will remain - currently it is hard to navigate away from
an open vifm instance with C-hjkl since it is not recognized as a vim
window anymore.
Additionally, invoking vim functions does not work from the vifm window,
which means that if I start nvim pointing to a directory, i.e. with vifm
open, it not possible for me currently to directly start up fzf to open
another file, or a buffer from the history, or similar.