add .pre-commit-config.yaml to expected files in checker

Signed-off-by: Côme Chilliet <come.chilliet@nextcloud.com>

build/files-checker.php

@@ -39,6 +39,7 @@ $expectedFiles = [
 	'.mailmap',
 	'.npmignore',
 	'.php-cs-fixer.dist.php',
+	'.pre-commit-config.yaml',
 	'.scrutinizer.yml',
 	'.tag',
 	'.tx',