Add schema to blueprint and update (#2)

* Blueprint: Add schema
* Update blueprint to fit schema

Author: ockham

assets/blueprints/blueprint.json

@@ -1,22 +1,15 @@
 {
+	"$schema": "https://playground.wordpress.net/blueprint-schema.json",
 	"landingPage": "/wp-admin/admin.php?page=html-api-debugger&html=<h1>Hello world!</h1>",
 	"preferredVersions": {
 		"php": "8.0",
 		"wp": "latest"
 	},
-	"phpExtensionBundles": ["kitchen-sink"],
 	"steps": [
 		{
 			"step": "login",
-			"username": "admin",
-			"password": "password"
-		},
-		{
-			"step": "installPlugin",
-			"pluginZipFile": {
-				"resource": "wordpress.org/plugins",
-				"slug": "html-api-debugger"
-			}
+			"username": "admin"
 		}
-	]
+	],
+	"plugins": ["html-api-debugger"]
 }