Chore: Add Automatic-Module-Name to JAR manifest

[tanya732]

Summary

• Adds Automatic-Module-Name: com.auth0.jwks to the JAR manifest
• Provides a stable JPMS module name for downstream consumers without requiring a full module-info.java

Context

This adds Java Module System support.

We opted for Automatic-Module-Name over a full MRJAR approach because:

• The library targets Java 8
• There is only one package (com.auth0.jwk)
• Internal classes are already package-private