Implement OCI image spec

[CertainLach]

What type of PR is this?

/kind api-change
/kind bug
/kind cleanup
/kind dependency-change
/kind deprecation
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #20

Special notes for your reviewer:

Does this PR introduce a user-facing change?

None

[openshift-ci-robot]

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[CertainLach]

Seems like this spec is already implemented in https://github.com/ecarrara/oci-registry-client

[CertainLach]

Implementation in #26 will use https://github.com/ecarrara/oci-registry-client