chore(php-cs-fixer): ignore node_modules

[st3iny]

Ignore node_modules when running php-cs-fixer (e.g. composer run cs:check).

Before

1 unrelated error! 😢

   1) node_modules/flatted/php/flatted.php
      ---------- begin diff ----------
--- /home/richard/src/nextcloud/master/dev_apps/contacts/node_modules/flatted/php/flatted.php
+++ /home/richard/src/nextcloud/master/dev_apps/contacts/node_modules/flatted/php/flatted.php

After

No errors! 😃