Support empty workflow yaml files

[guettli]

Act version

act version 0.2.50

Feature description

Sometimes we comment out github worklow yaml files compleletly, so that they don't get executed.

But then act -l fails:

❯ act -l
Error: unable to read workflow 'empty.yml': file is empty: EOF

It would be nice if act -l would work, even if there are empty workflow files.

[silverwind]

What does GitHub actions do with such files? Throw an error or silently ignore it?

[guettli]

What does GitHub actions do with such files? Throw an error or silently ignore it?

I got not error from Github. The file got ignored, that's why I opened this issue.

[silverwind]

Ok, yes then it makes sense for act to ignore it as well.