minimal doc changes for v3

[pwright]

No description provided.

[pwright]

@jsenko I'm moving operator docs to here, see Apicurio/apicurio-registry-operator#257 also

[jsenko]

Thanks, I have a few questions / notes:

• Do we want to keep the Registry and Operator docs separated? I don't have a strong opinion on this, depends on your preference.

• A lot of the pages are not applicable yet, at least until after the TP. We should keep (with some updates) the following topics:

  • Installation
  • Storage / Persistence information
  • Managing env. variables
  • PodTemplateSpec
  • Managed resources
  • CR spec and status overview.

  and add basic information about the 3 components: Registry API, Registry UI, Studio UI. I'll try to help with this if I have time.