[+] i18n SSR

src/app.d.ts

@@ -1,13 +1,15 @@
 // See https://svelte.dev/docs/kit/types#app.d.ts
 // for information about these interfaces
 declare global {
-	namespace App {
-		// interface Error {}
-		// interface Locals {}
-		// interface PageData {}
-		// interface PageState {}
-		// interface Platform {}
-	}
+  namespace App {
+    // interface Error {}
+    interface Locals {
+      lang: 'en' | 'zh'
+    }
+    // interface PageData {}
+    // interface PageState {}
+    // interface Platform {}
+  }
 }
 
 export {};