Update CI badge

Author: eldruin

README.md

@@ -1,6 +1,6 @@
 # gpio-cdev
 
-[![Build Status](https://travis-ci.org/rust-embedded/gpio-cdev.svg?branch=master)](https://travis-ci.org/rust-embedded/gpio-cdev)
+[![Build Status](https://github.com/rust-embedded/gpio-cdev/workflows/Build/badge.svg)](https://github.com/rust-embedded/gpio-cdev/actions)
 [![Version](https://img.shields.io/crates/v/gpio-cdev.svg)](https://crates.io/crates/gpio-cdev)
 [![License](https://img.shields.io/crates/l/gpio-cdev.svg)](https://github.com/rust-embedded/gpio-cdev/blob/master/README.md#license)