Expose access-token-jwt library, so this package could be used without express

[stajkowski]

Checklist

• I have looked into the Readme and Examples, and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

Publish access-token-jwt as a separate package. This allows customers to create their own middleware in various frameworks.

Describe the ideal solution

Publish access-token-jwt as a separate package.

Alternatives and current workarounds

No alternatives that are ideal and clean solutions.

Additional context

No additional context required, self-explanatory.

[stajkowski]

Additionally, ugly solution detailed in #75 does not work for Cloudflare Workers due to unsupported packages being installed with express-oauth2-jwt-bearer