[Proposal]Saga pattern support in Dapr workflow

[skyao]

According to Yaron's suggestion, this proposal is moved to dapr/proposals repo.

See:

• Add saga pattern support in Dapr workflow proposals#48
• Add saga pattern support in Dapr workflow proposals#47

[skyao]

@yaron2 @artursouza please help to review this proposal of Saga pattern support. Thank you!

[skyao]

Close this issue since it's moved to dapr/proposals repo.