#1: Drupal 9 readiness

composer.json

@@ -21,6 +21,7 @@
     }
   ],
   "require": {
+    "drupal/core": "^8 || ^9",
     "npm-asset/lazysizes": "^4.1"
   }
 }

lazysizes.info.yml

@@ -2,6 +2,7 @@ name: Lazysizes
 description: Integrates lazysizes plugin into Drupal.
 type: module
 core: 8.x
+core_version_requirement: ^8 || ^9
 package: Field Formatters
 dependencies:
   - drupal:responsive_image