svelte.config.js: Unexpected option config.kit.vite

I just started learning Svelte/kit, I stated a small project to learn, I wanted a calendar. I found svelte-calendar package in npm. I installed the package,

npm i svelte-calendar

And I set this in svelte.config.js

import adapter from '@sveltejs/adapter-auto';const config = {    kit: {        adapter: adapter(),        vite: {            optimizeDeps: {                include: ['just-throttle', 'dayjs']            }        }    }};export default config;

Why am I getting this error when I run

npm run dev

This is my fist time working with Svelte-kit and npm so I don't have much idea on this.