Add documentation link towards enrollment json

[mschiessl]

Walking through the CLI documentation i find it quite hard to understand the Json struct of a new enrollment request.

I highly assume it might be this one (taken from the API docs)
https://developer.akamai.com/api/core_features/certificate_provisioning_system/v2.html#postenrollments
but i'd appreciate if this could be added to the sources or at least referenced within the documentation.

[vreddhi]

Thank you for the feedback @mschiessl . We will evaluate and incorporate this in next release.