Support firebase/jwt ^6

I guess I'd be open to bumping to JWT 6.x, but I imagine you've seen that Zoom is deprecating JWT completely in June. https://www.drupal.org/project/zoomapi/issues/3283888 🌱 The JWT app type will be completely deprecated as of June 2023 Fixed

I'm currently working on a 3.x version that supports the Server-to-server app type (the replacement for JWT apps).

I'll do some testing with JWT 6.x and see if I notice any regressions.

I took a minute to try about JWT 6.x and didn't see any regressions. This module's usage is super minimal (only the encode method). Looking at the 6.x release notes, I didn't see any concerns around backwards compatibility issues with the encode method. https://github.com/firebase/php-jwt/releases/tag/v6.0.0

Feel free to take it for a spin and let me know if it works for you.

2.0.x Version is no longer viable because of Zoom API changes. Closing.