feat: Add support for direct public key JWT verification without JWKS discovery

[ankita10119]

Description

This PR adds support for directly providing a public key for JWT verification without requiring JWKS discovery or endpoints, addressing issue #133.

Currently, the library only supports:

1. Using issuerBaseURL to fetch JWKS via discovery
2. Manually providing jwksUri and issuer
3. Symmetric keys via string secret

This change extends the secret parameter to accept KeyLike objects (public keys from Node's crypto module), enabling asymmetric JWT verification without network
dependencies.

• Fixes publicKey without discovery #133

  Changes

  Core Implementation:

  • Updated JwtVerifierOptions.secret type from string to string | KeyLike
  • Modified validation logic in jwt-verifier.ts to distinguish between string secrets (symmetric) and KeyLike objects (asymmetric)
  • Updated get-key-fn.ts to handle KeyLike objects directly without conversion
  • Exported KeyLike type for user convenience

Testing

Describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

Please include any manual steps for testing end-to-end or functionality not covered by unit/integration tests.

Also include details of the environment this PR was developed in (language/platform/browser version).

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch