Update README.md

Author: javadev

README.md

@@ -7,6 +7,7 @@ underscore-java11
 [![codecov](https://codecov.io/gh/javadev/underscore-java11/branch/master/graph/badge.svg)](https://codecov.io/gh/javadev/underscore-java11)
 [![Quality Gate](https://sonarcloud.io/api/project_badges/measure?project=javadev_underscore-java11&metric=alert_status)](https://sonarcloud.io/dashboard/index/javadev_underscore-java11)
 [![Quality Gate](https://sonarcloud.io/api/project_badges/measure?project=javadev_underscore-java11&metric=sqale_rating)](https://sonarcloud.io/dashboard/index/javadev_underscore-java11)
+[![](http://javadoc-badge.appspot.com/com.github.javadev/underscore11.svg?label=JavaDocs)](http://www.javadoc.io/doc/com.github.javadev/underscore11/)
 [![Build Status](https://dev.azure.com/javadevazure/underscore-java/_apis/build/status/javadev.underscore-java11)](https://dev.azure.com/javadevazure/underscore-java/_build/latest?definitionId=5)
 ![Java Version](https://img.shields.io/badge/java-%3E%3D%2011-success)