Update README.md Swift version

Author: s4cha

README.md

@@ -1,7 +1,7 @@
 ![Stevia](https://raw.githubusercontent.com/s4cha/Stevia/master/banner.png)
 
 [![Documentation](https://img.shields.io/badge/Read_the-Docs-67ad5c.svg)](https://freshos.github.io/SteviaDocs/)
-[![Language: Swift 2, 3, 4 and 5](https://img.shields.io/badge/language-swift%205-f48041.svg?style=flat)](https://developer.apple.com/swift)
+[![Language: Swift 2, 3, 4, 5 and 6](https://img.shields.io/badge/language-swift%206-f48041.svg?style=flat)](https://developer.apple.com/swift)
 ![Platform: iOS 8+](https://img.shields.io/badge/platform-iOS%20|%20tvOS-blue.svg?style=flat)
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![CocoaPods compatible](https://img.shields.io/badge/Cocoapods-compatible-4BC51D.svg?style=flat)](https://cocoapods.org/pods/SteviaLayout)