use github actions for build badge

.github/workflows/build.yml

@@ -1,4 +1,4 @@
-name: TinyUSB CI
+name: Build
 
 on: [pull_request, push]
 

README.md

@@ -2,7 +2,7 @@
 
 ![tinyUSB_240x100](https://user-images.githubusercontent.com/249515/62646655-f9393200-b978-11e9-9c53-484862f15503.png)
 
-[![Build Status](https://travis-ci.org/hathach/tinyusb.svg?branch=master)](https://travis-ci.org/hathach/tinyusb) [![License](https://img.shields.io/badge/license-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT) [![Coverity](https://img.shields.io/coverity/scan/458.svg)](https://scan.coverity.com/projects/tinyusb)
+[![Build Status](https://github.com/hathach/tinyusb/workflows/Build/badge.svg)](https://travis-ci.org/hathach/tinyusb) [![License](https://img.shields.io/badge/license-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT) [![Coverity](https://img.shields.io/coverity/scan/458.svg)](https://scan.coverity.com/projects/tinyusb)
 
 TinyUSB is an open-source cross-platform USB Host/Device stack for embedded system, designed to be memory-safe with no dynamic allocation and thread-safe with all interrupt events are deferred then handled in the non-ISR task function.