[Update] Use flexible bridge address and update README for the demo (#111)

When the user open the demo page remotely, it need to update the
up-board IP to run the demo. This is inconvenient and not necessary.
We can use window.location.hostname to fix it.

Author: qiuzhong

demo/README.md

@@ -36,10 +36,7 @@ $ npm install
 $ npm install -g http-server
 ```
 
-## Run demo
-### Update the web bridge up
-Get the Up-board Squared IP address, and update it in [index.html](./index.html) at line 84: replace `127.0.0.1` to the IP
-
+## Run the demo
 ### Start up MicroRTPSAgent
 New a terminal session, run
 ```
@@ -64,8 +61,7 @@ $ http-server -c-1
 ```
 
 ### Try to control the robot remotely
-Now you can put the TurtleBot3 robot on the ground. Let another PC at the same wireless network, then open the browser on this PC and enter:
-`http://<up-board ip>:8080`. After the page loaded, you can press the `Up/Left/Right/Down` buttons to control the robot remotely.
+Now you can put the TurtleBot3 robot on the ground. Let another PC be in the same wireless network, then launch the browser and enter: `http://<up-board ip>:8080`. After the page loaded, you can press the `Up/Left/Right/Down` buttons to control the robot remotely.
 
 ## Known limitation:
 If you shutdown the MicroRTPSAgent utility, you have to reset the OpenCR before you launch it again.

demo/index.html

@@ -79,7 +79,7 @@
 	<script src="js/controller.js"></script>
 	<script>
 		let ros = new ROSLIB.Ros();
-		let bridgeHost = '127.0.0.1';
+		let bridgeHost = window.location.hostname;
 		let bridgePort = 9090;
 
 		ros.on('connection', function() {