chore: reorganize docs apps (#7228)

* reorganize docs apps

* add README

* fix directory

* add condition for old docs

www/apps/book/components/EditButton/index.tsx

@@ -0,0 +1,16 @@
+"use client"
+
+import { EditButton as UiEditButton } from "docs-ui"
+import { usePathname } from "next/navigation"
+
+const EditButton = () => {
+  const pathname = usePathname()
+
+  return (
+    <UiEditButton
+      filePath={`/www/apps/book/app${pathname.replace(/\/$/, "")}/page.mdx`}
+    />
+  )
+}
+
+export default EditButton