Update README.md

Display Support for Swift Package Manager with badge in readme!

README.md

@@ -6,6 +6,7 @@
 [![CocoaPods compatible](https://img.shields.io/cocoapods/v/UIFontComplete.svg)](#cocoapods)
 [![CocoaPods](https://img.shields.io/cocoapods/dt/UIFontComplete.svg)]()
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
+ [![Swift Package Manager compatible](https://img.shields.io/badge/Swift%20Package%20Manager-compatible-brightgreen.svg)](https://github.com/apple/swift-package-manager)
 [![License](http://img.shields.io/:license-mit-blue.svg)](http://doge.mit-license.org)
 
 Make working with `UIFont` faster and less error-prone