[Enhancement] Support firebase/php-jwt version 6

[pmartin35]

Does this library support firebase/php-jwt version 6? composer.json requires "firebase/php-jwt":">=5.0.0" but it seems the upgrade to version 6 has quite a few breaking changes:

firebase/php-jwt version 6 was released in 2022 and the composer.json for this project has not been updated since 2019. So I think this might lead to incompatibilities.

Describe the solution you'd like
Confirmation whether this library supports firebase/php-jwt v6? If not, locking to version 5: "firebase/php-jwt":"^5.0".