Pass CancellationToken To RunAsync and ReadAsync

[khalidabuhakmeh]

Use case(s)

Some processes are long-running tasks, and the ability to kill these processes might be a good thing. I have a process that starts playing an audio file and I'd like to stop the audio with a cancellationToken.

Description

            var audio = await SimpleExec.Command.ReadAsync(
                "afplay",
                string.Join(" ", arguments),
                noEcho: true,
                cancellationToken: cancellationToken
            );

The issue is that the cancellation request needs to call process.Kill or else the process continues to run in the background.

Alternatives

Handroll starting a process.

Additional context

I'll try and make an attempt myself at implementing the change, but my async foo is mediocre at best.

[adamralph]

Re-opening this, to consider whether Run and Read should also accept a CancellationToken as per @danielmarbach's suggestion in #238.

[adamralph]

Decided to support CancellationToken only in the async methods, and not in the sync methods.

[adamralph]

Released in 6.4.0-rc.1.

@khalidabuhakmeh please give it a try.