Allow contributors to set workflow::blocked label
In some occasions, we contributors might need to change the workflow
label to something other that workflowin dev and workflowin review. workflowblocked in particular could be very handy.
An example is gitlab-org/gitlab!98979 (merged), where I wanted to set the workflow label to workflowblocked since I need to work on something else before continuing the work on that MR.