feat: update json method in Response interface to accept JSON type

dist/router.d.ts

@@ -18,7 +18,7 @@ export interface Response extends ServerResponse {
         body: string;
     }) => void;
     status: (code: number) => Response;
-    json: (body: string, code?: number) => void;
+    json: (body: JSON, code?: number) => void;
     html: (body: string, code?: number) => void;
     redirect: (target: string, code?: number) => void;
 }