Replace demo.html with the serial terminal-based demo (#52)

* Mention serial terminal demo in README.md

* Delete the old demo

README.md

@@ -1,10 +1,18 @@
 # Serial API Polyfill
 
-An implementation of the [Serial API](https://wicg.github.io/serial) on top of
-the [WebUSB API](https://wicg.github.io/webusb) for use with USB-to-serial
+An implementation of the [Web Serial API](https://wicg.github.io/serial) on top
+of the [WebUSB API](https://wicg.github.io/webusb) for use with USB-to-serial
 adapters. Use of this library is limited to hardware and platforms where the
 device is accessible via the WebUSB API because it has not been claimed by a
-built-in device driver. This project will be used to prototype the design of
-the Serial API.
+built-in device driver. This project was used to prototype the design of
+the Web Serial API and remains useful for platforms (such as Android) which
+support the WebUSB API but do not support the Web Serial API.
 
-This is also available as an npm package [here](https://www.npmjs.com/package/web-serial-polyfill) for convenience.
+This is also available as an npm package
+[here](https://www.npmjs.com/package/web-serial-polyfill) for convenience.
+
+A demo of this library is provided as part of the
+[serial terminal demo](https://github.com/GoogleChromeLabs/serial-terminal)
+and can be activated by clicking the
+"[Switch to API polyfill](https://googlechromelabs.github.io/serial-terminal/?polyfill)"
+link.