Updates README and adds an example for volumeClaim testing usage

[ionicc]

What does this PR do?

• Adds a volumeClaim example: config/samples/k6_v1alpha1_k6_with_volumeClaim.yaml.
• Updates the readme with a more thorough explanation on how to use volumeClaims and also adds a directory example.

Why?

• After taking some time debugging and experimenting with running k6 tests using volumeClaims, I believe having more concrete examples and explanations like this would help folks working with it in the future.

[CLAassistant]

All committers have signed the CLA.

[yorugac]

@ionicc Thank you a lot for this PR! No doubt that it'll definitely be helpful 👍 😄

I have a bit of change request; could you please update it?

[yorugac]

Custom image is not a requirement for volumeClaim: could you please remove it from the example? So that there's no confusion about it.

[ionicc]

@yorugac Thanks for noticing that, Removed it now!

[yorugac]

Suggested change

	In the above example, `test.js` imports a function from `stress-test.js` and, They would look like this:
	In the above example, `test.js` imports a function from `stress-test.js` and they would look like this:

[ionicc]

@yorugac Nicely observed, Fixed!

[yorugac]

@ionicc Great, thanks for the update!

[patenvy1234]

how to create a volume claim pls explain

[yorugac]

@patenvy1234, creating volumes and volume claims is part of standard Kubernetes docs:
https://kubernetes.io/docs/tasks/configure-pod-container/configure-persistent-volume-storage/#create-a-persistentvolume
There're also a lot of third-party guides and howto's in the network about it.

[patenvy1234]

I am using --out csv option as an arugment to get csv output from each pod but as the pods are unaccessible I am not able to get those CSV outputs will PVC help me here or is there any other simpler option ?

[patenvy1234]

I have already created volume claim now how store the test.js inside it ? and what should be the mounting location