fixed user not adding to localStorage

frontend/src/logic/sdk.ts

@@ -9,13 +9,11 @@ export function signup(username: string, password: string)
     db.users = JSON.stringify({})
 
   const users = JSON.parse(db.users)
-  
   if (users[username])
-    throw new Error('Username already exists')
+    throw new Error('User already exists')
 
   users[username] = password
   db.users = JSON.stringify(users)
-
 }
 
 export function login(username: string, password: string)