Revise repository documentation for registry-operator

[michael-valdron]

Which area/kind this issue is related to?

/area documentation
/area registry
/area releng

Issue Description

A review and revising of all the documentation in registry-operator, including READMEs. This includes adding missing instructions, updating outdated information and separation of documentation where it makes sense.

Acceptance Criteria

• README
• CONTRIBUTING

[michael-valdron]

Rest of the acceptance criteria needs completion.

[thepetk]

Putting it in a later date for refinement as some more criteria should be defined :) Also updating the status to waiting
cc @michael-valdron