Add 'allow-plugins' section to composer.json

[lukaszachy]

Without this section, current latest composer 2.10.0 fails with

In PluginManager.php line 746:

  Your composer.lock was generated before the allow-plugins security feature
  was introduced and your composer.json does not define allow-plugins. Run "c
  omposer update --lock" locally and commit the updated composer.lock, then a
  dd an explicit allow-plugins section to composer.json. See https://getcompo
  ser.org/allow-plugins

Hit this in today's ubi8/php-74 refresh.