Update validator keys page

[emmanuel-awosika]

Description

• Added information about EIP-7002 (a proposal that will allow validators sign exit messages with their withdrawal keys)
• Added an article on validator key management

[netlify]

❌ Deploy Preview for ethereumorg failed.

Name	Link
🔨 Latest commit	fcdd9c3
🔍 Latest deploy log	https://app.netlify.com/sites/ethereumorg/deploys/67be354c0c484b00088f7c7a

[github-actions]

This issue is stale because it has been open 30 days with no activity.

[gitguardian]

️✅ There are no secrets present in this pull request anymore.

If these secrets were true positive and are still valid, we highly recommend you to revoke them.
While these secrets were previously flagged, we no longer have a reference to the
specific commits where they were detected. Once a secret has been leaked into a git
repository, you should consider it compromised, even if it was deleted immediately.
Find here more information about risks.

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