Use GitHub Actions CI badges (#970)

Author: timvaillancourt

README.md

@@ -1,6 +1,6 @@
 # gh-ost
 
-[![build status](https://travis-ci.org/github/gh-ost.svg)](https://travis-ci.org/github/gh-ost) [![downloads](https://img.shields.io/github/downloads/github/gh-ost/total.svg)](https://github.com/github/gh-ost/releases) [![release](https://img.shields.io/github/release/github/gh-ost.svg)](https://github.com/github/gh-ost/releases)
+[![ci](https://github.com/github/gh-ost/actions/workflows/ci.yml/badge.svg)](https://github.com/github/gh-ost/actions/workflows/ci.yml) [![replica-tests](https://github.com/github/gh-ost/actions/workflows/replica-tests.yml/badge.svg)](https://github.com/github/gh-ost/actions/workflows/replica-tests.yml) [![downloads](https://img.shields.io/github/downloads/github/gh-ost/total.svg)](https://github.com/github/gh-ost/releases) [![release](https://img.shields.io/github/release/github/gh-ost.svg)](https://github.com/github/gh-ost/releases)
 
 #### GitHub's online schema migration for MySQL <img src="doc/images/gh-ost-logo-light-160.png" align="right">