Add documentation on OIDC public key (JWKS) requirements for Tenant IdP Configuration

[lamw]

I found the documentation in configuring OIDC IdP for Tenant Portal to be quite light when needing to specify your own JWKS. After a bit of trial/error, I was able to figure it out (thanks to ChatGPT) and have put together the following https://williamlam.com/2025/10/configuring-vcf-automation-vcfa-organization-portal-oidc-idp-using-terraform-provider-for-vcfa.html which might be useful to enhance the existing documentation to provide a bit more details on how to use it with TF provider