docs(v2): _index docs page does not show a sidebar (#2839)

* docs: _index docs page does not show a sidebar

Closes #2836

* Update website/docs/docs.md

Co-authored-by: Alexey Pyltsyn <lex61rus@gmail.com>

Co-authored-by: Alexey Pyltsyn <lex61rus@gmail.com>

website/docs/docs.md

@@ -55,7 +55,7 @@ Given the example above, now when you navigate to the path `/docs` you will see
 
 :::important
 
-The document id of `_index` is reserved exclusively for the home doc page, so it will not work as a standalone route.
+The document id of `_index` is reserved exclusively for the home doc page, so it will not work as a standalone route. If left to the default, the page will not show a sidebar. If you wish to have a sidebar for this page, specify the document id that is listed in the sidebar file.
 
 :::