Update README.md

Author: alexito4

README.md

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 # Flow
 
+[![Swift](https://github.com/alexito4/Flow/actions/workflows/swift.yml/badge.svg)](https://github.com/alexito4/Flow/actions/workflows/swift.yml)
+
 🌊 Let your code *flow*.
 
 This library provides a bunch of extension methods for a better fluent syntax in Swift. This style is very useful for some operations that benefit from being able to be chained (composed) together.