contributors: Add SIG ContribEx as owners

[justaugustus]

@kubernetes/sig-contributor-experience-leads — I've noticed a few PRs e.g., #7691, #7923 that are flagging @kubernetes/steering-committee members for review, when we likely don't need to be in the path.

Raising this PR draw attention to the approval gap.
Let me know if you want me to extend it to other directories or if you're happy to carry any updates as follow-ups.

[justaugustus]

/hold until SIG ContribEx reviews

[MadhavJivrajani]

/lgtm
with SIG ContribEx hat on

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: justaugustus, MadhavJivrajani

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Needs approval from an approver in each of these files:

• OWNERS [MadhavJivrajani,justaugustus]

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[pacoxu]

/hold until SIG ContribEx reviews

/unhold

[MadhavJivrajani]

/hold

[MadhavJivrajani]

For other leads in case they have any comments, can unhold after one more ack.

[mbianchidev]

Ah, didn't notice that my PR was set for the steering committee to review, whoops. Sorry about that.

Btw, in case someone (else) wants to merge it feel free, we have had some people wonder how to sign the CLA when they start contributing :)

[Priyankasaggu11929]

/lgtm (as ContribEx TL)

/unhold