Please make those utils crossplatform

[Emasoft]

It would be great to also have a crossplatform version of all those utils. The majority of file management operations are the same in every OS, and one of the Dart strengths lies in its in very portable code, even better than Node.js.

[azenla]

I'll try, most of it is, except for things like:

• sync
• whoami

Because they call native functions only on Unix based systems. I develop on a Mac, so everything works on there, the biggest problem is Windows.