Allow migrate_plus 6 (#88)

Co-authored-by: Christian Fritsch <christian.fritsch@burda.com>

Author: chrfritsch

composer.json

@@ -12,7 +12,7 @@
 	}
   ],
   "require": {
-	"drupal/migrate_plus": "^4.0 || ^5.0",
+	"drupal/migrate_plus": "^4.0 || ^5.0 || ^6.0",
 	"digicol/dcx-sdk-php": "^2.0"
   },
   "require-dev": {