fix(seo): use || instead of ?? for sitemap hostname fallback

?? only falls back on null/undefined; an empty string (the default in
.env.example) would pass through as the hostname and produce an invalid
sitemap. || also handles empty strings.

Author: gabitoesmiapodo

vite.config.ts

@@ -14,7 +14,7 @@ export default defineConfig({
     react(),
     tsconfigPaths(),
     Sitemap({
-      hostname: process.env.PUBLIC_APP_URL ?? 'https://demo.dappbooster.dev',
+      hostname: process.env.PUBLIC_APP_URL || 'https://demo.dappbooster.dev',
     }),
   ],
   build: {