Ceph deployment documentation

[lae]

The Ceph configuration section in the README is a bit lackluster and requires the user to parse through the example provided themselves - of which some might not even be needed for some users. Ideally, this section should provide steps and explanations along the way for configuring PVE Ceph with the help of this role.

I haven't exactly used this feature myself, so it might be best for someone who has experience with this use case to write said documentation.