add CLA

Author: fanweixiao

README.md

@@ -145,3 +145,9 @@ More examples in `/examples/`
 
 ## License
 [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fyomorun%2Fy3-codec-golang.svg?type=large)](https://app.fossa.com/projects/git%2Bgithub.com%2Fyomorun%2Fy3-codec-golang?ref=badge_large)
+
+## CLA
+
+[Sign CLA](https://cla-assistant.io/yomorun/y3-codec-golang)
+
+[![CLA assistant](https://cla-assistant.io/readme/badge/yomorun/y3-codec-golang)](https://cla-assistant.io/yomorun/y3-codec-golang)