chore: add license

[varunsrin]

Motivation

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Change Summary

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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

Additional Context

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PR-Codex overview

This PR updates the project's LICENSE.md file to include the MIT License terms and copyright information for 2020-2024.

Detailed summary

• Added the MIT License terms
• Included copyright information for 2020-2024
• Defined permissions for using the software
• Stated conditions for usage
• Clarified warranty disclaimer and liability statement

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[github-actions]

Coverage after merging varunsrin/license into main will be

100.00%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
Bundler.sol	100%	100%	100%	100%
FnameResolver.sol	100%	100%	100%	100%
IdGateway.sol	100%	100%	100%	100%
IdRegistry.sol	100%	100%	100%	100%
KeyGateway.sol	100%	100%	100%	100%
KeyRegistry.sol	98.61%	94.44%	100%	100%	153, 153
RecoveryProxy.sol	100%	100%	100%	100%
StorageRegistry.sol	100%	100%	100%	100%
src/abstract
EIP712.sol	100%	100%	100%	100%
Guardians.sol	100%	100%	100%	100%
Migration.sol	96.97%	90%	100%	100%	40
Nonces.sol	100%	100%	100%	100%
Signatures.sol	100%	100%	100%	100%
src/validators
SignedKeyRequestValidator.sol	100%	100%	100%	100%