Feature reques: Add output in "unified diff" format.

[hacker-DOM]

This might be a stupid question, but would it be possible to --output unified-diff? That way it would be really easy to integrate it with existing tools like Magit and Lazygit. To paraphrase, how much of difftastic's superpowers would we lose if we do that?

[llllvvuu]

Same as https://github.com/Wilfred/difftastic/issues/186 I think

(The answer to "how much of difftastic's superpowers would we lose if we do that?" seems to be "some")

[texastoland]

integrate it with existing tools like Magit and Lazygit

Not to derail the issue but Lazygit provides specialized integration!