feat: Support for zsh

[grzesuav]

Checklist

1. Adresses Issue: Make kubectl-prompt suitable for use with zsh #9
2. Quick summary of changes
   POC of new helper function definition
3. Changes are GNU/BSD Compatable:yes
4. Changes are applicable to the wider community: yes
5. Request help with testing if needed: yes

[grzesuav]

This is POC for now. I am not bash/zsh programmer so I am not aware of consequences. I tested this function locally on bash and zsh and it was working for me, but I have too limited knowledge to see bigger context

[grzesuav]

please do not merge

[Jefferson-Faseler]

@grzesuav Hey! I branched off of you and opened another PR so you wouldn't have to play middleman and we go through two PR's to get it here. You can find the PR here:
#27

Of course left your fingerprints on the commits, lmk if you have any questions.

[grzesuav]

no problem, good that you had time to carry this work :)