chore: reorganize docs apps (#7228)

* reorganize docs apps

* add README

* fix directory

* add condition for old docs

www/apps/book/config/index.ts

@@ -0,0 +1,8 @@
+import { DocsConfig } from "types"
+import { sidebarConfig } from "./sidebar"
+
+export const config: DocsConfig = {
+  titleSuffix: "Medusa Book",
+  baseUrl: process.env.NEXT_PUBLIC_BASE_URL || "http://localhost:3000",
+  sidebar: sidebarConfig,
+}