update to nextra 3

next.config.js

@@ -1,12 +1,13 @@
-const withNextra = require('nextra')({
+import nextra from 'nextra'
+
+const withNextra = nextra({
   theme: 'nextra-theme-docs',
   themeConfig: './theme.config.jsx',
 })
 
-module.exports = {
-  ...withNextra(),
+export default withNextra({
   output: 'export',
   images: {
     unoptimized: true,
   },
-}
+})