Update badge image on shield.io to Swift 5

Author: mattia-duckma

README.md

@@ -5,7 +5,7 @@
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-[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](#carthage) [![CocoaPods compatible](https://img.shields.io/cocoapods/v/ReactiveSwift.svg)](#cocoapods) [![SwiftPM compatible](https://img.shields.io/badge/SwiftPM-compatible-orange.svg)](#swift-package-manager) [![GitHub release](https://img.shields.io/github/release/ReactiveCocoa/ReactiveSwift.svg)](https://github.com/ReactiveCocoa/ReactiveSwift/releases) ![Swift 4.2](https://img.shields.io/badge/Swift-4.2-orange.svg) ![platforms](https://img.shields.io/badge/platform-iOS%20%7C%20macOS%20%7C%20tvOS%20%7C%20watchOS%20%7C%20Linux-lightgrey.svg)
+[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](#carthage) [![CocoaPods compatible](https://img.shields.io/cocoapods/v/ReactiveSwift.svg)](#cocoapods) [![SwiftPM compatible](https://img.shields.io/badge/SwiftPM-compatible-orange.svg)](#swift-package-manager) [![GitHub release](https://img.shields.io/github/release/ReactiveCocoa/ReactiveSwift.svg)](https://github.com/ReactiveCocoa/ReactiveSwift/releases) ![Swift 5.0](https://img.shields.io/badge/Swift-5.0-orange.svg) ![platforms](https://img.shields.io/badge/platform-iOS%20%7C%20macOS%20%7C%20tvOS%20%7C%20watchOS%20%7C%20Linux-lightgrey.svg)
 
 🎉 [Getting Started](#getting-started) 🚄 [Release Roadmap](#release-roadmap)