Add playground blueprint and live demo badge

Add blueprints/demo.json to provide a WordPress Playground blueprint that auto-logs in (admin/password), installs and activates the plugin from the repository ZIP, and targets PHP 8.0 + latest WP. Update readme.md to include a Live Demo badge linking to the new blueprint URL so users can quickly launch the demo environment.

Author: boopathirbk

blueprints/demo.json

@@ -0,0 +1,25 @@
+{
+    "$schema": "https://playground.wordpress.net/blueprint-schema.json",
+    "landingPage": "/wp-admin/admin.php?page=wp-bulk-pages-generator",
+    "preferredVersions": {
+        "php": "8.0",
+        "wp": "latest"
+    },
+    "steps": [
+        {
+            "step": "login",
+            "username": "admin",
+            "password": "password"
+        },
+        {
+            "step": "installPlugin",
+            "pluginData": {
+                "resource": "url",
+                "url": "https://github.com/boopathirbk/wp-bulk-pages-generator/archive/refs/heads/main.zip"
+            },
+            "options": {
+                "activate": true
+            }
+        }
+    ]
+}

readme.md

@@ -6,6 +6,7 @@
 
   **Deploy Landing Pages, SEO Silos, and Content Batches in Seconds with the Speed of Geist.**
 
+  [![Live Demo](https://img.shields.io/badge/Live-Demo-blue?style=for-the-badge&logo=wordpress)](https://playground.wordpress.net/?blueprint-url=https://raw.githubusercontent.com/boopathirbk/wp-bulk-pages-generator/main/blueprints/demo.json)
   [![Latest Release](https://img.shields.io/github/v/release/boopathirbk/wp-bulk-pages-generator?style=for-the-badge&color=2271b1&label=Version)](https://github.com/boopathirbk/wp-bulk-pages-generator/releases/latest)
   [![Download Latest](https://img.shields.io/badge/Download-Latest%20.ZIP-success?style=for-the-badge&logo=github)](https://github.com/boopathirbk/wp-bulk-pages-generator/releases/latest/download/wp-bulk-pages-generator.zip)
   [![WCAG 2.2 AA](https://img.shields.io/badge/A11y-WCAG%202.2%20AA-success?style=for-the-badge)](https://www.w3.org/WAI/standards-guidelines/wcag/)