Case insensitive redirects

## Prerequisites

* [x] I am running the latest version. (`up upgrade`)
* [x] I searched to see if the issue already exists.
* [x] I inspected the verbose debug output with the `-v, --verbose` flag.
* [x] Are you an Up Pro subscriber?

## Description

In migrating over to UP and Hugo at the same time I am getting a lot of 404 issues with pages and inbound links. It comes down to the case of the URL. For example:

* `https://site.com/posts/Foo` returns 404 because the new page is `https://site.com/posts/foo` (lower case).

Is there some trick in the up.json rewrites to make the requested URL downcase? I don't want to have to input every page on my site to have an all lower value in the up.json file.