docs: tidy Proxy wallet README

[TetrisIsCute]

Summary

• Improve wording in the Proxy wallet examples README.
• Align heading style and terminology with the Safe wallet docs.
• Add a link back to the main README for additional context.
  Notes
• Documentation-only change in examples/proxyWallet/README.md.

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Note

Documentation-only update to examples/proxyWallet/README.md.

• Standardizes capitalization/terminology ("Proxy wallet") and punctuation
• Improves wording for clarity
• Adds link to main README for Safe/Proxy wallet context

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[TetrisIsCute]

This mirrors the Safe wallet README tidy-up: it aligns the heading and wording for Proxy wallets and links back to the main README so both example folders feel consistent for new builders.