fix(api, client): update Gatsby, webpack & related things (#41452)

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

client/gatsby-config.js

@@ -1,17 +1,13 @@
 const path = require('path');
-
-const {
-  clientLocale,
-  curriculumLocale,
-  homeLocation
-} = require('../config/env.json');
-
+const envData = require('../config/env.json');
 const {
   buildChallenges,
   replaceChallengeNode,
   localeChallengesRootDir
 } = require('./utils/buildChallenges');
 
+const { clientLocale, curriculumLocale, homeLocation } = envData;
+
 const curriculumIntroRoot = path.resolve(__dirname, './src/pages');
 const pathPrefix =
   clientLocale === 'english' || clientLocale === 'chinese'
@@ -84,20 +80,20 @@ module.exports = {
         }
       }
     },
-    {
-      resolve: `gatsby-plugin-advanced-sitemap`,
-      options: {
-        exclude: [
-          `/dev-404-page`,
-          `/404`,
-          `/404.html`,
-          `/offline-plugin-app-shell-fallback`,
-          `/learn`,
-          /(\/)learn(\/)\S*/
-        ],
-        addUncaughtPages: true
-      }
-    },
+    // {
+    //   resolve: `gatsby-plugin-advanced-sitemap`,
+    //   options: {
+    //     exclude: [
+    //       `/dev-404-page`,
+    //       `/404`,
+    //       `/404.html`,
+    //       `/offline-plugin-app-shell-fallback`,
+    //       `/learn`,
+    //       /(\/)learn(\/)\S*/
+    //     ],
+    //     addUncaughtPages: true
+    //   }
+    // },
     {
       resolve: 'gatsby-plugin-manifest',
       options: {