Issue #3116498 by mglaman: Allow installation with Drupal 9

composer.json

@@ -7,7 +7,7 @@
     "homepage": "https://www.drupal.org/project/jsonapi_resources",
     "minimum-stability": "dev",
     "require": {
-      "drupal/core": "^8.8@alpha"
+      "drupal/core": "^8.8 || ^9.0"
     }
   }