I previously had an alias defined as `simple_vim`, which would start an instance
of Vim with a bare bones config. I had a to-do to Nixify it. That is
now (mostly) to-done.
When I try and install it with `nix-env -f ~/briefcase -iA tools.simple_vim`,
Nix fails and says that pkgs.stdenv is undefined. I will need to fix this one
day, but it is neither important nor urgent...
