chore: reorganize docs apps (#7228)

* reorganize docs apps

* add README

* fix directory

* add condition for old docs

www/apps/book/.env.sample

@@ -0,0 +1,17 @@
+NEXT_PUBLIC_SEGMENT_API_KEY=
+NEXT_PUBLIC_DOCS_ALGOLIA_INDEX_NAME=
+NEXT_PUBLIC_API_ALGOLIA_INDEX_NAME=
+NEXT_PUBLIC_ALGOLIA_API_KEY=
+NEXT_PUBLIC_ALGOLIA_APP_ID=
+NEXT_PUBLIC_ENV=
+NEXT_PUBLIC_BASE_URL=
+NEXT_PUBLIC_RESOURCES_URL=
+NEXT_PUBLIC_USER_GUIDE_URL=
+NEXT_PUBLIC_UI_URL=
+NEXT_PUBLIC_API_URL=
+ALGOLIA_WRITE_API_KEY=
+ANALYZE_BUNDLE=
+NEXT_PUBLIC_AI_ASSISTANT_URL=
+NEXT_PUBLIC_AI_WEBSITE_ID=
+NEXT_PUBLIC_AI_API_ASSISTANT_RECAPTCHA_SITE_KEY=
+CLOUDINARY_CLOUD_NAME=