docs: update intro in README.md

Author: hantsy

README.md

@@ -1,2 +1,52 @@
 # angular-spring-rsocket-sample
-Demo for using Angular and Spring RSocket together
+
+This sample is to demonstrate a chat application using the following cutting-edge technology stack :
+
+* Angular as client which uses `rsocket-js` to communicate with the server side
+* Spring WebFlux based RSocket server which uses WebSocket as transport protocol
+* Spring Data MongoDB based  `@Tailable`  query result as an infinite stream
+
+## Build
+
+Before running the application, you should build and run client and server side respectively.
+
+### Server
+
+Run a MongoDB service firstly, simply you can run it from a Docker container. There is a `docker-compose.yaml` file is ready for you.
+
+```bash
+docker-compose up mongodb
+```
+
+Build the application.
+
+```e
+./gradlew build
+```
+
+Run the target jar from the *build* folder to start up the application.
+
+```bash
+java -jar build/xxx.jar
+```
+
+### Client
+
+Install dependencies.
+
+```bash
+npm install
+```
+
+Start up the application.
+
+```bash
+npm run start
+```
+
+Open a browser and  navigate to http://localhost:4200.
+
+
+## Reference
+
+* [rsocket-js samples](https://github.com/rsocket/rsocket-js/blob/master/packages/rsocket-examples)