docs: add routing page (#9550)

- Add a new homepage to `book` project for the routing page
- Move all main doc pages to be under `/v2/learn` (and added redirects + fixed links across docs)
- Other: add admin components to resources dropdown + fixes to search on mobile.

Closes DX-955

Preview: https://docs-v2-git-docs-router-page-medusajs.vercel.app/v2

www/apps/book/app/learn/storefront-development/nextjs-starter/page.mdx

@@ -0,0 +1,67 @@
+import { Prerequisites, BetaBadge } from "docs-ui"
+
+export const metadata = {
+  title: `${pageNumber} Next.js Starter`,
+}
+
+# {metadata.title} <BetaBadge text="Beta" tooltipText="The Next.js Starter is currently in development to fully support Medusa v2." />
+
+In this chapter, you’ll learn how to install and use the Next.js Starter storefront.
+
+## Install Next.js Starter
+
+<Prerequisites items={[
+  {
+    text: "Node.js v20+",
+    link: "https://nodejs.org/en/download"
+  },
+  {
+    text: "At least one region in the Medusa application.",
+  },
+]} />
+
+1. Clone the `v2` branch of the [Next.js Starter](https://github.com/medusajs/nextjs-starter-medusa/tree/v2):
+
+```bash
+git clone https://github.com/medusajs/nextjs-starter-medusa -b v2 my-medusa-storefront
+```
+
+2. Change to the `my-medusa-storefront` directory, install the dependencies, and rename the template environment variable:
+
+```bash npm2yarn
+cd my-medusa-storefront
+npm install
+mv .env.template .env.local
+```
+
+3. While the Medusa application is running, start the Next.js storefront:
+
+```bash npm2yarn
+npm run dev
+```
+
+Your Next.js Starter Storefront is now running at `localhost:8000`.
+
+---
+
+## Customize Storefront
+
+To customize the storefront, refer to the following directories:
+
+- `src/app`: The storefront’s pages.
+- `src/modules`: The storefront’s components.
+- `src/styles`: The storefront’s styles.
+
+<Note title="Tip">
+
+You can learn more about development with Next.js through [their documentation](https://nextjs.org/docs/getting-started).
+
+</Note>
+
+---
+
+## Configurations and Integrations
+
+The Next.js Starter is compatible with some Medusa integrations out-of-the-box, such as the Stripe provider module. You can also change some of its configurations if necessary.
+
+Refer to the [Next.js Starter reference](!resources!/nextjs-starter) for more details.