Allow Laravel 13

[danielsdeboer]

Adds Laravel 13 support.

Combines the changes from #46 (by @Team-Nifty-GmbH) with the missing CI coverage and docs:

• Widen illuminate/support and illuminate/database constraints to ^12.0|^13.0, and orchestra/testbench to ^10.0|^11.0 (from Allow Laravel 13 #46).
• Add Laravel 13 (testbench ^11.0) to the CI matrix. Excludes PHP 8.2 × Laravel 13 since Laravel 13 requires PHP 8.3+.
• Update README to note version 5.0 supports Laravel 12 and 13.

Supersedes #46.