chore(style): add missing strict declaration

Author: gaetan-hexadog

config/config.php

@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     /*
     |--------------------------------------------------------------------------

pint.json

@@ -9,6 +9,7 @@
         },
         "concat_space": {
             "spacing": "one"
-        }
+        },
+        "declare_strict_types": true
     }
 }