Provide a way to uninstall

[Astrantia]

I can't find uninstall instructions in the repository. @Parth

[Parth]

so take a look at what deploy does.

To uninstall you can:

1. uninstall whichever your system didn't have prior to deploy (for example a system might have vim and tmux, but not zsh. Deploy installs zsh, track this and uninstall just zsh).
2. Figure out what the old shell was and change back to that shell
3. To delete the dotfiles you just need to delete the dotfile folder

Pull requests are welcome.

[Parth]

Perhaps this is better as a section in the readme