Jwt-auth: Add Laravel 7 support

[iforwms]

Subject of the issue

Current dependencies not satisfied by Laravel 7.

Your environment

| Q | A
| ----------------- | ---
| Bug? | no
| New Feature? | yes
| Framework | Laravel
| Framework version | 7.0.0
| Package version | 1.0.0-rc5.1
| PHP version | 7.4.0

Steps to reproduce

Try and upgrade Laravel to version 7.0.0.

Expected behaviour

Composer update should complete sucessfully.

Actual behaviour

Dependency error

tymon/jwt-auth 1.0.0-rc.5.1 requires illuminate/support ^5.1|^6 

Updating composer dependencies to allow illuminate/support ^7.

[alijmlzd]

Please add Laravel 7 support or provide a temporary solution.

[erikn69]

Please add Laravel 7 support

[p4scu41]

I wanted to test the new Laravel 7 but I wasn't able, it would be great to add the support.

[gerardnll]

Please @tymondesigns it would be great if you can merge any of the PRs about this, Thanks.