feat(blueprint): add WordPress Playground blueprint

Adds a WordPress Playground blueprint configuration and a "Test with WordPress Playground" badge to the README. This allows users to preview the plugin's iframe block functionality in a live environment with a pre-configured demo page.

Author: firestar300

.wordpress-org/blueprints/blueprint.json

@@ -0,0 +1,32 @@
+{
+	"$schema": "https://playground.wordpress.net/blueprint-schema.json",
+	"landingPage": "/blockparty-iframe-demo/",
+	"preferredVersions": {
+		"php": "8.1",
+		"wp": "latest"
+	},
+	"steps": [
+		{
+			"step": "installPlugin",
+			"pluginData": {
+				"resource": "git:directory",
+				"url": "https://github.com/BeAPI/blockparty-iframe",
+				"ref": "1.1.1",
+				"refType": "tag"
+			},
+			"options": {
+				"activate": true,
+				"targetFolderName": "blockparty-iframe"
+			}
+		},
+		{
+			"step": "login",
+			"username": "admin",
+			"password": "password"
+		},
+		{
+			"step": "runPHP",
+			"code": "<?php require_once 'wordpress/wp-load.php'; $page_content = '<!-- wp:blockparty/iframe {\"title\":\"Johannes Gutenberg — Wikipédia\",\"url\":\"https://en.wikipedia.org/wiki/Johannes_Gutenberg\",\"align\":\"wide\"} -->\n<div class=\"wp-block-blockparty-iframe alignwide\"><iframe title=\"Johannes Gutenberg — Wikipédia\" src=\"https://en.wikipedia.org/wiki/Johannes_Gutenberg\" loading=\"eager\"></iframe></div>\n<!-- /wp:blockparty/iframe -->'; $page_id = wp_insert_post( array( 'post_title' => 'Blockparty Iframe', 'post_name' => 'blockparty-iframe-demo', 'post_content' => $page_content, 'post_status' => 'publish', 'post_type' => 'page' ) ); echo 'Page created with ID: ' . $page_id; ?>"
+		}
+	]
+}

README.md

@@ -1,5 +1,7 @@
 # Blockparty — Iframe
 
+[![Test with WordPress Playground](https://img.shields.io/badge/Test%20with-WordPress%20Playground-0073aa?style=for-the-badge&logo=wordpress&logoColor=white)](https://playground.wordpress.net/?blueprint-url=https://raw.githubusercontent.com/beapi/blockparty-iframe/refs/heads/main/.wordpress-org/blueprints/blueprint.json)
+
 [![License: GPL v2](https://img.shields.io/badge/License-GPL%20v2-blue.svg)](https://www.gnu.org/licenses/gpl-2.0)
 [![WordPress: 6.7+](https://img.shields.io/badge/WordPress-6.7+-green.svg)](https://wordpress.org/)
 [![PHP: 8.1+](https://img.shields.io/badge/PHP-8.1+-purple.svg)](https://php.net/)