OWNERS: add operator-sdk reviewers estroz, joelanford, jmrodri

[estroz]

Description of the change: add @estroz, @joelanford, and @jmrodri as reviewers

Motivation for the change: operator-sdk uses a bunch of operator-registry libraries, and given its commitment to stability within major version releases would like to ensure the backwards-compatibility of these libraries. This includes contributing work that ensures compatibility.

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /docs
• Commit messages sensible and descriptive

[estroz]

/cc @dinhxuanvu

[dinhxuanvu]

/lgtm

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dinhxuanvu, estroz

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