Add toggle theme button and remove old css files

pages/api/hello.ts

@@ -1,13 +0,0 @@
-// Next.js API route support: https://nextjs.org/docs/api-routes/introduction
-import type { NextApiRequest, NextApiResponse } from 'next'
-
-type Data = {
-  name: string
-}
-
-export default function handler(
-  req: NextApiRequest,
-  res: NextApiResponse<Data>
-) {
-  res.status(200).json({ name: 'John Doe' })
-}