Fix typos

[Dimitrolito]

This PR addresses minor typographical issues and improves phrasing in the README.md file of the auth-client package. These changes enhance the readability and accuracy of the documentation.

Change Summary

• Corrected "framework agnostic" to "framework-agnostic" for consistency and adherence to standard English.
• Replaced "an wallet client" with "a wallet client" to use the proper article.

Merge Checklist

• PR title adheres to the conventional commits standard.
• PR has a changeset.
• PR has been tagged with a change label(s) (documentation).
• PR includes documentation if necessary.
• All commits have been signed.

Additional Context

These changes are minimal but improve the clarity and professionalism of the documentation for developers using the auth-client library.