feat: nushell table output mode

> This is basically just a re-creation of [the following issue from the original repo](https://github.com/ogham/exa/issues/1182) but in this fork :)

Original issue by @galop1n

Nushell is a modern take on shell. Nushell's table approach to every thing is neat, and their core ls take on the matter is already an improvement or the old way.

eza remains a more advanced ls replacement, and it would be terrific to have a nushell compatible output, for example with eza --nu that can be pipe the way nushell intends.

I saw a request for structured eza output that kind of overlap with that request, but felt dissociate enough to open the new issue.

@eggbean had suggested that adding a `--json` option would be good, like the [tre](https://github.com/dduan/tre)e replacement tre has.

The issue does not name files, tests, or entry points. Start by reviewing eza's existing output-format and structured-output handling, then compare the original issue and Nushell's expected table input. Done means a defined Nushell-compatible mode, such as eza --nu, that can be piped as intended and is covered by appropriate output tests.

Written by the indexing model from the issue text.