chore: add example in readme

Author: SSebo

README.md

@@ -8,7 +8,25 @@
 FeatureProbe is an open source feature management service. This SDK is used to control features in JavaScript programs. This
 SDK is designed primarily for use in multi-user systems such as web servers and applications.
 
-## Getting started
+## Try Out Demo Code
+
+We provide a runnable demo code for you to understand how FeatureProbe SDK is used.
+
+1. Start FeatureProbe Service with docker composer. [How to](https://github.com/FeatureProbe/FeatureProbe#1-starting-featureprobe-service-with-docker-compose)
+2. Download this repo and run the demo program:
+```bash
+git clone https://github.com/FeatureProbe/client-sdk-js.git
+cd client-sdk-js
+// open example/index.html in browser
+```
+
+3. Find the Demo code in [example](https://github.com/FeatureProbe/client-sdk-js/tree/main/example), 
+do some change and run the program again.
+```
+// open example/index.html in browser
+```
+
+## Step-by-Step Guide
 
 In this guide we explain how to use feature toggles in a JavaScript application using FeatureProbe.
 
@@ -74,8 +92,6 @@ test("feature probe unit testing", (done) => {
 });
 ```
 
-[Here is an example](https://github.com/FeatureProbe/client-sdk-js/tree/main/example)
-
 ## Available options
 
 This SDK takes the following options:
@@ -95,7 +111,7 @@ We have unified integration tests for all our SDKs. Integration test cases are a
 be sure to pull submodules first to get the latest integration tests before running tests.
 
 ```js
-    npm run test
+npm run test
 ```
 
 ## Contributing