added short example

docs/documentation/chrome-har/index.md

@@ -16,3 +16,23 @@ twitterdescription:
 Create [HAR](http://www.softwareishard.com/blog/har-12-spec/) files based on [Chrome Debugging Protocol](https://developer.chrome.com/devtools/docs/debugger-protocol) data.
 
 Code originally extracted from [Browsertime](https://github.com/sitespeedio/browsertime), initial implementation inspired by [Chromedriver_har](https://github.com/woodsaj/chromedriver_har).
+
+
+## Introduction
+
+Chrome-HAR is for tool makers: Get the log from the Chrome Debugging Protocol and use Chrome-HAR to parse it to a HAR.
+
+## Example
+
+Convert your messages to a HAR file.
+
+~~~
+const parser = require('chrome-har');
+
+// you already have the message from Chrome Debugging Protocol
+
+parser.harFromMessages(messages))
+ .then(har => {
+   // do whatever you want with the HAR file
+ })
+~~~