feat: Add netlify adapter to demo

Author: t0yohei

demo/astro.config.mjs

@@ -1,5 +1,9 @@
 // @ts-check
 import { defineConfig } from 'astro/config';
 
+import netlify from '@astrojs/netlify';
+
 // https://astro.build/config
-export default defineConfig({});
+export default defineConfig({
+  adapter: netlify()
+});

demo/package.json

@@ -9,6 +9,7 @@
     "astro": "astro"
   },
   "dependencies": {
+    "@astrojs/netlify": "^6.2.0",
     "astro": "^5.3.0",
     "astro-qiita-loader": "../"
   }