add delta view to taplo-cli

[drahnr]

It's not uncommon to use a formatter in CI where a subset of contributors do not have the tool installed. That set of contributors is usually very appreciative of direct cues what to fix.

The changes:

Adds a dependency to prettydiff and ansi_term for creating the diff and coloring, there is currently (almost) no clustering of diff lines, this is to be improved.

[tamasfe]

I think this could be gated behind a flag like --diff as this can get very verbose, looks good otherwise, thanks!

[drahnr]

Added --diff flag, both for --check and non-check. Introduced a scope macro echo! that utilizes self.env. I think it's ready for another review pass :)

[tamasfe]

Looks great, thank you!