minor #4976 Add instructions for PHPStan (julienfalque)
minor #4976 Add instructions for PHPStan (julienfalque)

This PR was merged into the 2.15 branch.

Discussion
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Add instructions for PHPStan

Commits
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05bdd168 Add instructions for PHPStan

kubawerlos/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,GrahamCampbell/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,keradus/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,keradus/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer