Add support for zsh

[NedkoHristov]

As title says - add zsh support. Otherwise I cannot run the project on my Apple Air M2.
One more thing - if I try to run it trough bash I got (on latest OS with all updates passed and brew upgrade as well):

BASH version 4.2+ required to run sshto, your is - 3.2.57(1)-release

Thanks.

[APT256]

Try this: https://www.unindented.org/blog/change-shell-to-latest-bash-on-macos/