Command.ExecuteAsync stdout and stderr content now gets returned

[YanikCeulemans]

This is an initial attempt at fixing the Command.ExecuteAsync not properly returning the the stdout content. I have updated the tests to return Async<Unit> so the results are awaited.

Fixes #57

[YanikCeulemans]

I have not yet tested the failure cases when the command fails to execute or times out given a cancellation token.

Please feel free to comment / edit wherever necessary.

Thanks in advance for your time.

[CaptnCodr]

Thank you for your PR.
After reviewing and trying out and running tests locally the CancelAfter operation doesn't work anymore.
Handlers OutputDataReceived and ErrorDataReceived were added for this purpose.

Do you have another idea how to solve this?

[CaptnCodr]

I have something here. I apply it to this PR soon.

[CaptnCodr]

Does this look good to you?

[YanikCeulemans]

Looks good to me! I ran the tests on my macOS machine and they all passed.

Thank you very much for your time and effort.

[CaptnCodr]

@YanikCeulemans this fix has been deployed in v1.10.1 and is already available at Nuget.
Thank you for your contribution! ❤️