chore: add links to audit reports

[horsefacts]

Motivation

Add audit reports to README.

Merge Checklist

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• The PR title adheres to the conventional commits standard
• The PR has been tagged with change type label(s) (i.e. documentation, feature, bugfix, or chore)
• The PR's changes adhere to all the requirements in the contribution guidelines
• All commits have been signed

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PR-Codex overview

This PR focuses on adding information about audits for the v3 contracts.

Detailed summary

• Added section for audits
• Included links to audit reports A-1 and A-2 from 0xMacro

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[github-actions]

Coverage after merging horsefacts/add-audit-reports into main will be

98.66%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
Bundler.sol	100%	100%	100%	100%
FnameResolver.sol	100%	100%	100%	100%
IdRegistry.sol	100%	100%	100%	100%
KeyRegistry.sol	100%	100%	100%	100%
RecoveryProxy.sol	100%	100%	100%	100%
StorageRegistry.sol	100%	100%	100%	100%
src/lib
EIP712.sol	50%	100%	50%	50%	19
Signatures.sol	100%	100%	100%	100%
TransferHelper.sol	0%	0%	0%	0%	12, 17, 20, 20, 20
TrustedCaller.sol	100%	100%	100%	100%
src/validators
SignedKeyRequestValidator.sol	100%	100%	100%	100%