add maven central badge

Author: eaxdev

README.md

@@ -1,6 +1,7 @@
 # Java JsonResume Validator
 [![Build Status](https://github.com/eaxdev/Java-JsonResume-Validator/workflows/build/badge.svg)](https://github.com/eaxdev/Java-JsonResume-Validator/actions)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/eaxdev/Java-JsonResume-Validator/master/LICENSE)
+![Maven Central](https://img.shields.io/maven-central/v/io.github.eaxdev/jsonresume-validator)
 
 Java library to validate JSON resumes to ensure that they are according to the [defined schema](https://jsonresume.org/schema/)