Updated PS1 Setup to work with ZSH

[devppratik]

What type of PR is this?

documentation

What this PR does / Why we need it?

The export keyword was missing from the setup of kube-PS1 for ZSH which was causing the following warning anytime while logging into the cluster

WARN[0007] Env KUBE_PS1_CLUSTER_FUNCTION is not detected. It is recommended to set PS1 to learn which cluster you are operating on, refer https://github.com/openshift/backplane-cli/blob/main/docs/PS1-setup.md

Also the method mentioned in the docs for ZSH would work only when oh-my-zsh is added/enabled separately in zsh. I have added the process to enable this for vanilla zsh

Which Jira/Github issue(s) does this PR fix?

Resolves #

Special notes for your reviewer

Pre-checks (if applicable)

• Ran unit tests locally
• Validated the changes in a cluster
• Included documentation changes with PR

[codecov-commenter]

Codecov Report

Merging #202 (5467247) into main (26e1081) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #202   +/-   ##
=======================================
  Coverage   51.53%   51.53%           
=======================================
  Files          51       51           
  Lines        3415     3415           
=======================================
  Hits         1760     1760           
  Misses       1364     1364           
  Partials      291      291           

[openshift-ci]

@devppratik: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/scan-optional	5467247	link	false	/test scan-optional

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[samanthajayasinghe]

/lgtm

[feichashao]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: devppratik, feichashao, samanthajayasinghe

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