Fixes #5047.

extensions/gii/generators/extension/default/composer.json

 {
-	"name": "<?= $generator->vendorName ?>/<?= $generator->packageName ?>",
-	"description": "<?= $generator->description ?>",
-	"type": "<?= $generator->type ?>",
-	"keywords": <?= $generator->keywordsArrayJson ?>,
-	"license": "<?= $generator->license ?>",
-	"authors": [
-		{
-			"name": "<?= $generator->authorName ?>",
-			"email": "<?= $generator->authorEmail ?>"
-		}
-	],
-	"autoload": {
-		"psr-4": {
-			"<?= str_replace('\\','\\\\',$generator->namespace) ?>": ""
-		}
-	}
+    "name": "<?= $generator->vendorName ?>/<?= $generator->packageName ?>",
+    "description": "<?= $generator->description ?>",
+    "type": "<?= $generator->type ?>",
+    "keywords": <?= $generator->keywordsArrayJson ?>,
+    "license": "<?= $generator->license ?>",
+    "authors": [
+        {
+            "name": "<?= $generator->authorName ?>",
+            "email": "<?= $generator->authorEmail ?>"
+        }
+    ],
+    "require": {
+        "yiisoft/yii2": "*"
+    },
+    "autoload": {
+        "psr-4": {
+            "<?= str_replace('\\','\\\\',$generator->namespace) ?>": ""
+        }
+    }
 }