Update README.md

Author: danielgerlag

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 # Workflow Core
 
 [![Build status](https://ci.appveyor.com/api/projects/status/xnby6p5v4ur04u76?svg=true)](https://ci.appveyor.com/project/danielgerlag/workflow-core)
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 Workflow Core is a light weight embeddable workflow engine targeting .NET Standard.  Think: long running processes with multiple tasks that need to track state.  It supports pluggable persistence and concurrency providers to allow for multi-node clusters.