Add CI badge

README.md

-## Fluwx ![pub package](https://img.shields.io/pub/v/fluwx.svg)
+# Fluwx 
+![pub package](https://img.shields.io/pub/v/fluwx.svg)
+[![Build status](https://img.shields.io/cirrus/github/OpenFlutter/fluwx/master)](https://cirrus-ci.com/github/OpenFlutter/fluwx)
+======
 
 ![logo](./arts/fluwx_logo.png)
 

README_CN.md

-## FLuwx  ![pub package](https://img.shields.io/pub/v/fluwx.svg)
+# Fluwx 
+![pub package](https://img.shields.io/pub/v/fluwx.svg)
+[![Build status](https://img.shields.io/cirrus/github/OpenFlutter/fluwx/master)](https://cirrus-ci.com/github/OpenFlutter/fluwx)
+======
 
 ![logo](./arts/fluwx_logo.png)