Respect additional JSON paths from Laravel

[redelschaap]

Laravel allows a developer to register additional folders that contain JSON based translation files.

The Matice package did not respect these additional folders, causing a difference in the translations loaded server side and client side.

This PR adds support for additional JSON paths since Laravel 8.

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I also added Laravel 9 and additional PHP versions to the test suite. The current test suite does not support Laravel 10 or up because the PHPUnit configuration syntax is too old for the PHPUnit version used since Laravel 10. If it's fine to drop support for Laravel <= 8, I suppose it would be easier to write tests for newer Laravel versions.