Allow checksum verification of downloaded files

[tpasternak]

So it is possible to run scala-cli run https://gist.github.com/.... --checksum 1234567890abdef. If the checksum does not match the contents, then fail

[ghostbuster91]

I think that since the scala-cli relies on coursier to fetch artifacts the best option would be to add this feature directly to coursier and later reuse it in scala-cli.

There is an open issue in coursier repository about that: https://github.com/coursier/coursier/issues/1131

I will try to move it forward.

It would be great if someone from scala-cli team could verify that approach.

[romanowski]

@ghostbuster91 I think this is the right approach.