Update the readme about Swift Package Manager

Author: dreampiggy

README.md

@@ -2,9 +2,11 @@
 
 A wrapper for [libwebp](https://github.com/webmproject/libwebp) + Xcode project.
 This enables Carthage support
+This also contains the Swift Package Manager support
 
 [![CI Status](http://img.shields.io/travis/SDWebImage/libwebp-Xcode.svg?style=flat)](https://travis-ci.org/SDWebImage/libwebp-Xcode)
 [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/SDWebImage/libwebp-Xcode)
+[![SwiftPM compatible](https://img.shields.io/badge/SwiftPM-compatible-brightgreen.svg)](https://swift.org/package-manager/)
 
 ## Requirements
 
@@ -15,16 +17,47 @@ This enables Carthage support
 
 ## Installation
 
+### Carthage
+
 libwebp is (via this repo) available through [Carthage](https://github.com/Carthage/Carthage).
 
 ```
 github "SDWebImage/libwebp-Xcode"
 ```
 
+### SwiftPM
+
+Libwebp is available through [Swift Package Manager](https://img.shields.io/badge/SwiftPM-compatible-brightgreen.svg).
+
+```
+let package = Package(
+    dependencies: [
+        .package(url: "https://github.com/SDWebImage/libwebp-Xcode", from: "1.0.4")
+    ],
+    // ...
+)
+```
+
 ## Usage
 
 Use libwebp as you would normally, this is just a repo that adds an Xcode proj.
 
+For Swift Package Manager user, use the modular import instead of C headers.
+
++ Objective-C
+
+```objective-c
+@import libwebp;
+```
+
++ Swift
+
+```swift
+import libwebp
+```
+
 ## License
 
 libwebp is available under the BSD-3 license. See [the LICENSE file](https://github.com/webmproject/libwebp/blob/master/COPYING) for more info.
+
+