Make trailing directory backslash optional

### Description

I'd like trailing directory backslashes to be optional. I've done it manually on my local machine, and IMO it looks cleaner (esp when listing a directory with many subdirectories).

It looks like:

At the moment a space is conjoined to the end of file paths and a slash is conjoined to directory paths. I was thinking a flag could be used to make them uniform, or something similar.

This is strictly speaking a duplicate, since it's been asked for in the cited issue. I'm not fussed about the other elements of that request, though, just the backslashes.

I'd be happy to give it a go if deemed valuable.

- Relevant Issues : #344
- Relevant PRs : (none)
- Type of issue :
- [ ] Installation
- [ ] Font-related
- [x] Feature request
- [ ] Bug in existing feature
- [ ] Developer mode : Code quality / Tests / Documentation

Start by reading the CLI's path-formatting and directory-listing behavior, then compare this request with the cited issue #344. Determine how an optional flag should control trailing directory backslashes without changing file-path output; done means directory listings support the requested uniform formatting and the existing behavior remains available.

Written by the indexing model from the issue text.