Fix manifest addons format

CloudronManifest.json

@@ -3,15 +3,16 @@
   "title": "WordPress",
   "description": "WordPress is web software you can use to create a beautiful website or blog. We like to say that WordPress is both free and priceless at the same time.",
   "tagline": "Code is Poetry",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "dockerImage": "girish/wordpress:0.1.0",
   "healthCheckPath": "/",
   "httpPort": 80,
-  "addons": [
-    "mysql"
-  ],
   "manifestVersion": 1,
   "website": "https://wordpress.org/",
   "contactEmail": "apps@cloudron.io",
-  "icon": "icon.png"
+  "icon": "icon.png",
+  "addons": {
+    "mysql": {}
+  },
+  "minBoxVersion": "0.0.26"
 }