FR: Offer more specific URLs if current one has no posts

[ognsya]

This FR is the inverse of this one, and could complement it.

If the current URL has no posts, I'd like the option to see more specific URLs within it.

For example, lets say I'm at "www.bob.com", but that URL has no posts.
However, the URLs "www.bob.com/about" and "www.bob.com/pricing" do have posts.

I can think two ways this could be done:

1. The option to show all posts containing URLs starting with the current URL.
2. The option to first show a list of more specific URLs, which when clicked shows the posts for it.

Note this FR and the one linked at the top could then be combined in certain situations. For example, lets say I go to a website and I get the French version automatically, with the URL ending in "/fr", which has no Reddit posts for it. I would then get the option to check the more general URL (without the "/fr"), as well as any other variation (other languages for example).