Allow string in abandoned format as well, refs #4621

res/composer-schema.json

@@ -444,8 +444,8 @@
             }
         },
         "abandoned": {
-            "type": ["boolean"],
-            "description": "Indicates whether this package has been abandoned. Defaults to false."
+            "type": ["boolean", "string"],
+            "description": "Indicates whether this package has been abandoned, it can be boolean or a package name/URL pointing to a recommended alternative. Defaults to false."
         }
     }
 }