Renaming the variable from `initScript` to `bashAndZshInitScript` makes it clearer, what it is actually used for.
Moving the fish init script right below the other call to `thefuck --alias` makes it more obvious, when one of them is different in some important way.
The init script slightly differs depending on which shell is in use.
So for bash it should be in the interactiveShellInit as well.
In this case we don't need a mkIf as `bash` is enabled by default
on NixOS.
