ForTask Un-marshalled as DoTask

[reiniervl]

https://github.com/serverlessworkflow/sdk-go/blame/ff500a090258a53544b6e5451518d390e62936cc/model/task.go#L133

When un-marshalling a workflow that includes a ForTask, the task is un-marshalled as a DoTask, because the ForTask has the "do" key too, which is first in the list of the type registry. Placing the ForTask constructor with the "for" key above "do", would most likely fix the issue.

[ricardozanini]

@reiniervl I fixed this here: #224

As soon as I merge that PR should be fine :)

If you need it asap, you can open a PR with the fix.

[ricardozanini]

@reiniervl mind checking it again?