add webusb support to readme

Author: hathach

README.md

@@ -2,7 +2,7 @@
 
 [![Build Status](https://travis-ci.com/adafruit/Adafruit_TinyUSB_Arduino.svg?branch=master)](https://travis-ci.com/adafruit/Adafruit_TinyUSB_Arduino)[![License](https://img.shields.io/badge/license-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT)
 
-[TinyUSB](https://github.com/hathach/tinyusb) library for Arduino IDE. This library works with core platform that includes TinyUSB stack, typically you will see **Adafruit_TinyUSB_Core** inside core folder. Supported platform are:
+This library works with platform that includes [TinyUSB stack](https://github.com/hathach/tinyusb), typically you will see **Adafruit_TinyUSB_Core** inside core folder. Supported platform are:
 
 - [Adafruit_nRF52_Arduino](https://github.com/adafruit/Adafruit_nRF52_Arduino)
 - [Adafruit ArduinoCore-samd](https://github.com/adafruit/ArduinoCore-samd) **TinyUSB** must be selected in menu `Tools->USB Stack`
@@ -12,5 +12,6 @@ In addition to CDC that provided by the platform core, this library provide plat
 - Human Interface Device (HID): Generic (In & Out), Keyboard, Mouse, Gamepad etc ...
 - Mass Storage Class (MSC): with multiple LUNs
 - Musical Instrument Digital Interface (MIDI)
+- WebUSB with vendor specific class
 
 More document to write ...