fix: PATH update for non-fish shells
Reloading my shell config leads to duplication of path segments related to pyenv-virtualenv because the command:
eval "$(pyenv virtualenv-init -)"
which is part of my config, as per the README, is run without any checks of the current PATH being done in the background.
I've been experiencing this problem for many years but never had the time to look into it until now. Was surprised to not find any issues pointing out this problem, especially since the code has been around (unchanged) for so long, but found PR #430, in which another user fixed this problem for the fish shell a couple of years ago.
My PR looks to do the same for the catch-all case statement which follows the fish shell check. I'm not familiar with the code construct the other user used, so went with a statement that works for me in my zsh config. I'll note that I didn't test this in shells other than zsh, and also don't know enough about other shells and how they deal with bash scripts to be able to tell if this could not work in others.