Updated readme

Test Github action for tests (#17)

Fixes

* Fixed register JWTHandler

* Fixed dateTime claims

Added JsonTokenProvider.

Can be used to return tokens within the response body.

Allow php >= 8.0.0 and laravel 9 components.

lcobucci/jwt 4.0 upgrade (#13)

Upgrade lcobucci/jwt to 4.0 and using the new features.

JWT doesn't use Claim anymore but DataSet object instead.
JWTHandler requires Configuration instead of Builder, and Signer and registers a Key object instead of using the secret directly.
Requires nesbot/carbon ^2.0 for testability.

Laravel 8 support

fixed ServiceProviderTests

replaced deprecated methods of lcobucci/jwt

v2 for laravel ^7.0 and php >= 7.2.0