[feature request] Side-by-side diff similar to what's offered in vimdiff or vscode

[eris-price]

Micro has become my regular editor over the last year or so, but the lack of a diff mode has limited it's utility for me. I would love to be able to use it for all my terminal editor needs, but unfortunately, i need to keep other editors around because there's no good way to use micro as my DIFFPROG.