Wally should return error codes when an operation is not successful

[NobleDraconian]

Currently, as of v0.3.1, wally does not return any error codes when an operation fails. For example, if you run wally publish, but there is a version conflict, wally will fail the operation & spit an error message to the console. But it doesn't return an actual error code to the host process!

This makes things like github actions / CI proceed as if the operation were successful, when it wasn't:

[magnalite]

I agree, adding this should be a quick and easy win for ci/cd workflows