Adds SPM badge

Author: s4cha

README.md

@@ -3,6 +3,7 @@
 
 [![Language: Swift 5](https://img.shields.io/badge/language-swift5-f48041.svg?style=flat)](https://developer.apple.com/swift)
 ![Platform: iOS 9+](https://img.shields.io/badge/platform-iOS-blue.svg?style=flat)
+[![SPM compatible](https://img.shields.io/badge/SPM-compatible-4BC51D.svg?style=flat)](https://swift.org/package-manager/)
 [![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/Keyboard+LayoutGuide)
 [![Build Status](https://app.bitrise.io/app/0c1de450af273bff/status.svg?token=UpT-2PFMgu6h_RMRJW7PMQ&branch=master)](https://app.bitrise.io/app/0c1de450af273bff)