provide possibility to add prefix to the build process

next.config.js

-/** @type {import('next').NextConfig} */
+/** @type {import("next").NextConfig} */
 const nextConfig = {
   reactStrictMode: true,
+  basePath: process.env.APP_PREFIX ? process.env.APP_PREFIX + '/index.html' : '',
+  assetPrefix: process.env.APP_PREFIX ? process.env.APP_PREFIX + '/' : '',
   output: 'export',
   images: {
     unoptimized: true,