change: enable SS6 compatibility

Author: mleutenegger

composer.json

@@ -9,7 +9,7 @@
     ],
     "license": "BSD-3-Clause",
     "require": {
-        "silverstripe/framework": "^4 || ^5",
+        "silverstripe/framework": "^4 || ^5" || ^6",
         "silverstripe/admin": "^1.0 || ^2.0",
         "dnadesign/silverstripe-elemental": "^4 || ^5",
         "symbiote/silverstripe-gridfieldextensions": "^3 || ^4"