Rename header folder and update path in configuration

Renamed the folder 'resource' to 'resources' to better reflect its contents. Updated the file path in the PHP CS Fixer configuration accordingly to ensure continued functionality.

.php-cs-fixer.dist.php

@@ -120,6 +120,6 @@ $rules = array_merge(
     $untilFullSwitchToPhp8,
 );
 
-$rules['header_comment']['header'] = trim(file_get_contents(__DIR__.'/resource/header.txt'));
+$rules['header_comment']['header'] = trim(file_get_contents(__DIR__.'/resources/header.txt'));
 
 return $config->setRules($rules);