chore: Modify SITE_URL in Astro configuration to dynamically set based on NODE_ENV for improved local and production environment handling

Author: MaxiGarcia13

astro.config.js

@@ -5,7 +5,7 @@ import vercel from '@astrojs/vercel';
 import tailwindcss from '@tailwindcss/vite';
 import { defineConfig } from 'astro/config';
 
-const SITE_URL = process.env.VERCEL_URL
+const SITE_URL = process.env.NODE_ENV === 'production'
   ? `https://icon-sets-generator.vercel.app`
   : 'http://localhost:4321';