Update README

Author: kyleweiner

README.md

@@ -7,10 +7,22 @@ Sentiments is an iOS app written in Swift that analyzes text for positive or neg
 
 ## Usage
 
+### Sentiments
+
 1. Open `Sentiment-Analysis.xcworkspace`.
 2. Replace "YOUR_API_KEY" with your API key from [HPE Haven OnDemand](https://www.havenondemand.com) in [`AppConfig.swift`](https://github.com/kyleweiner/Sentiments/tree/master/Sentiment-Analysis/Constants/AppConfig.swift).
 3. Enter text in the text field and press the check button.
 
+### Highlight Sentiment Extension
+
+The project includes an experimental action extension for analyzing the sentiment of text on a web page. The extension behaves similarly to the containing app–positive sentiment is highlighted in green and negative sentiment is highlighted in red. 
+
+1. Launch Safari and navigate to a web page.
+2. Tap the share button.
+3. Tap the "Highlight Sentiment" icon.
+
+Note that the extension must first be enabled to complete step 3.
+
 ## Author
 
 Sentiments was written and designed by Kyle Weiner. It uses [Alamofire](https://github.com/Alamofire/Alamofire), [SwiftyJSON](https://github.com/SwiftyJSON/SwiftyJSON) and [HPE Haven OnDemand](https://dev.havenondemand.com/apis/analyzesentiment#overview)'s Sentiment Analysis API.