Add docs for new resources

[CodeBleu]

* Account
* Disk Offering
* Domain
* Kubernetes (version & Cluster)
* Network Offering
* Service Offering
* User
* Volume
* Zone

[yadvr]

Thanks for the docs @CodeBleu I couldn't thoroughly test all of them, but LGTM.

[CodeBleu]

Thanks @rohityadavcloud. I figured it was better than nothing. 😀 We can always go back and tweak it if needed.

[DaanHoogland]

just a side note , do these docs need apache license statements?

[yadvr]

@DaanHoogland I'm not sure, they never had license headers (https://github.com/apache/cloudstack-terraform-provider/tree/main/website/docs/r) and I'm not sure if adding those would somehow break the docs/website at https://registry.terraform.io/providers/cloudstack/cloudstack/latest/docs