add export WorkflowStepMiddlewareArgs

[sebaiturravaldes]

Summary

those exportables are not added

Requirements (place an x in each [ ])

• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've read and agree to the Code of Conduct.

[CLAassistant]

All committers have signed the CLA.

[misscoded]

Hi @siturra! Can you provide us with more information about the use case for exposing these internal bits? It will help us guide the review, as well as inform future work.

[misscoded]

Hi @siturra! Courtesy nudge: unless we hear back regarding more information about the use case for exposing these internal bits, we'll be closing this PR.

[seratch]

Let us close this PR now. Thanks again for your time here!