Adding 404 page to a custom path

Hi!

I would like to use a custom 404.html which is generated by Sphinx, but the file is not inserted on root level.

To be more specific, this file https://github.com/conan-io/docs/blob/gh-pages/en/latest/404.html should be used for default 404 error.

However, it does not, so I’ve added a default 404.html to redict: https://github.com/conan-io/docs/blob/gh-pages/404.html

Is there some way to do it, without that file on the root level? (I’m not using Jekyll).