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/packages/docs-ui/src/components/BorderedIcon/index.tsx

@@ -1,6 +1,7 @@
 import React from "react"
 import clsx from "clsx"
 import { IconProps } from "@medusajs/icons/dist/types"
+import Image from "next/image"
 
 export type BorderedIconProps = {
   icon?: string
@@ -29,9 +30,11 @@ export const BorderedIcon = ({
     >
       <span className={clsx("rounded-docs_xs", wrapperClassName)}>
         {!IconComponent && (
-          <img
+          <Image
             src={icon || ""}
-            className={clsx(iconClassName, "bordered-icon")}
+            className={clsx(iconClassName, "bordered-icon rounded-docs_xs")}
+            width={28}
+            height={28}
             alt=""
           />
         )}