Add PHP 8.5 support to CI testing

Update continuous integration workflow to test against PHP 8.5 by:
- Adding PHP 8.4 to the old_stable versions list
- Setting current_stable to 8.5

This ensures the package is tested and compatible with PHP 8.5.
Note that composer.json already supports PHP 8.5 via the ^8.0 constraint.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: koriym

.github/workflows/continuous-integration.yml

@@ -9,6 +9,6 @@ jobs:
   ci:
     uses: ray-di/.github/.github/workflows/continuous-integration.yml@v1
     with:
-      old_stable: '["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3"]'
-      current_stable: 8.4
+      old_stable: '["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4"]'
+      current_stable: 8.5
       script: demo/run.php