Silverstripe v6 support

Author: chrispenny

composer.json

@@ -16,12 +16,12 @@
     "issues": "https://github.com/chrispenny/silverstripe-dataobject-to-fixture/issues"
   },
   "require": {
-    "php": "^8.1",
-    "silverstripe/framework": "^5",
-    "silverstripe/cms": "^5"
+    "php": "^8.3",
+    "silverstripe/framework": "^6",
+    "silverstripe/cms": "^6"
   },
   "require-dev": {
-    "silverstripe/recipe-testing": "^3",
+    "silverstripe/recipe-testing": "^4",
     "slevomat/coding-standard": "^8"
   },
   "autoload": {