OKTA-242002-JWT iOS SDK: Add Carthage support

Author: IldarAbdullin-okta

README.md

@@ -13,12 +13,20 @@ This library handles decoding and validating a JSON Web Token (JWT) issued by an
 
 ## Installation
 
+### Cocoapods
+
 OktaJWT is available through [CocoaPods](http://cocoapods.org). To install it, simply add the following line to your Podfile:
 
 ```ruby
 pod 'OktaJWT'
 ```
 
+### Carthage
+
+To integrate this SDK into your Xcode project using [Carthage](https://github.com/Carthage/Carthage), specify it in your Cartfile:
+
+github "okta/okta-ios-jwt"
+
 ## Usage
 
 This library supports **validating** JWTs by extending the [JSONWebToken](https://github.com/kreactive/JSONWebToken) Swift library. By default, it will fetch the public keys from the OAuth 2.0 `/keys` endpoint of the specified authorization server, validate the JWT signature, and verify the token against given assertions.