feat(client): prefetch next challenge (#55472)

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

client/utils/declarations.d.ts

@@ -0,0 +1,11 @@
+declare global {
+  interface Window {
+    // This is a feature Gatsby adds to the `window` object.
+    // https://github.com/gatsbyjs/gatsby/blob/deb41cdfefbefe0c170b5dd7c10a19ba2b338f6e/packages/gatsby/cache-dir/production-app.js#L28
+    ___loader: {
+      hovering: (path: string | null) => void;
+    };
+  }
+}
+
+export {};

client/utils/gatsby/page-loading.ts

@@ -0,0 +1,10 @@
+/**
+ * The function is useful in cases where we want to preload a page
+ * but the link of the page isn't rendered on the screen.
+ * For more details, see https://github.com/freeCodeCamp/freeCodeCamp/pull/55472.
+ */
+export const preloadPage = (path: string | null) => {
+  if (!window.___loader || !path) return;
+
+  window.___loader.hovering(path);
+};