Update further reading section of validiums page

[emmanuel-awosika]

Description

• Added a comprehensive article analyzing the different types of rollups, including newer designs like sovereign rollups (validiums are similar to sovereign rollups with validity proofs and off-chain data availability)
• Added a Vitalik article on exit games for EVM validiums

[netlify]

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[github-actions]

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

[gitguardian]

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