Add PHP 8.6 to the CI matrix

[Copilot]

Extend the PHP versions tested in CI through PHP 8.6.

• PHPUnit matrix: Add 8.6; keep coverage and PHPStan on 8.5.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.21%. Comparing base (bd00669) to head (68c497a).

Additional details and impacted files

@@            Coverage Diff            @@
##               main      #26   +/-   ##
=========================================
  Coverage     99.21%   99.21%           
  Complexity      502      502           
=========================================
  Files           186      186           
  Lines          1019     1019           
=========================================
  Hits           1011     1011           
  Misses            8        8           

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[BenMorel]

@copilot Please also update brick/coding-standard to v6 (both in github actions and in the ecs composer.json)

[Copilot]

@copilot Please also update brick/coding-standard to v6 (both in github actions and in the ecs composer.json)

Updated both references to v6 in commit 68c497a.