Prettier diffing/expect output

[matanlurey]

See tap-difflet for NodeJS.

[matanlurey]

(By the way, I have need for something like this outside of the scope of just testing utilities - for example for printing debug messages in the console for Angular - if this means we need a package:diff, let me know, I'd love to help contribute)

[nex3]

How does it handle colors on Windows, or other situations where terminal colors are unavailable? I'm particularly curious about the string diff, where it seems like color is the only way the diff is communicated.

[nex3]

I decided not to make this milestone 1.0.0. I think it's important, but because it's largely independent of the API I don't want to block 1.0.0 on getting it fully-baked (or conversely, rush this to get 1.0.0 out the door). We should make sure the new 1.0.0 APIs make it possible to move to output like this without backwards-incompatibility, but we don't have to make that move immediately.

[matanlurey]

Sounds good, just nice to have for the future. Flutter might collaborate, they might want this too fwiw.