chore: Add CI badge in README (#245)

Author: u5surf

README.md

@@ -1,6 +1,7 @@
 Nginx virtual host traffic status module
 ==========
 
+[![CI](https://github.com/vozlt/nginx-module-vts/actions/workflows/ci.yml/badge.svg)](https://github.com/vozlt/nginx-module-vts/actions/workflows/ci.yml)
 [![License](http://img.shields.io/badge/license-BSD-brightgreen.svg)](https://github.com/vozlt/nginx-module-vts/blob/master/LICENSE)
 
 Nginx virtual host traffic status module