[TASK] Add extension-key to composer.json

composer.json

@@ -19,5 +19,10 @@
 		"psr-4": {
 			"T3o\\Randombanners\\": "Classes"
 		}
+	},
+	"extra": {
+		"typo3/cms": {
+			"extension-key": "randombanners"
+		}
 	}
 }