chore(deps): Support PHP 8.5 and Laravel 13

[KentarouTakeda]

This pull request provides:

• Support Laravel 13
• Add tests for PHP 8.5 to CI
• Update GitHub Actions to latest versions
  • actions/checkout v4 → v6
  • release-please-action migrate to googleapis org (archived google-github-actions)

[KentarouTakeda]

@TartanLeGrand
Laravel 13 has officially been released. Could you take a look at this PR?

[KentarouTakeda]

Hi @TartanLeGrand, @Jorgagu — gentle follow-up here.

Laravel 13 has been GA for a couple of months now and the constraint in this package is starting to block a few of my projects. This PR is small (composer + CI matrix bumps), CI is green, and GitHub
reports it as mergeable — so it should be a low-effort merge whenever one of you has a few minutes.

Completely understand maintaining OSS in spare time. If there's anything I can do to make merging easier — rebasing, splitting commits, addressing review feedback, or helping with maintenance more
broadly — please just let me know. Happy to take on whatever is most useful.

Thanks for keeping this library going!