Add doc [skip ci].

Author: vuongxuongminh

README.md

@@ -1,7 +1,7 @@
 # JWT Payload Extractor
 
-![example workflow](https://github.com/php-istio/jwt-payload-extractor/actions/workflows/unit-tests.yml/badge.svg)
-![example workflow](https://github.com/php-istio/jwt-payload-extractor/actions/workflows/coding-standards.yml/badge.svg)
+![unit tests](https://github.com/php-istio/jwt-payload-extractor/actions/workflows/unit-tests.yml/badge.svg)
+![coding standards](https://github.com/php-istio/jwt-payload-extractor/actions/workflows/coding-standards.yml/badge.svg)
 [![codecov](https://codecov.io/gh/php-istio/jwt-payload-extractor/branch/main/graph/badge.svg?token=I2ZACWOYHM)](https://codecov.io/gh/php-istio/jwt-payload-extractor)
 [![Latest Stable Version](http://poser.pugx.org/php-istio/jwt-payload-extractor/v)](https://packagist.org/packages/php-istio/jwt-payload-extractor)