README.md: add Maven central version badge

Author: PetrHeinz

README.md

@@ -5,6 +5,7 @@
 [![Better Stack dashboard](https://github.com/logtail/logback-logtail/assets/10132717/0b7a6c84-1499-4d43-b3e6-f3b40285d627)](https://betterstack.com/logs)
 
 [![MIT License](https://img.shields.io/badge/license-MIT-blue)](LICENSE.md)
+[![Maven com.logtail:logback-logtail](https://maven-badges.herokuapp.com/maven-central/com.logtail/logback-logtail/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.logtail/logback-logtail)
 [![Java Build](https://github.com/logtail/logback-logtail/actions/workflows/java_build.yaml/badge.svg?branch=main)](https://github.com/logtail/logback-logtail/actions/workflows/java_build.yaml)
 
 Experience SQL-compatible structured log management based on ClickHouse. [Learn more ⇗](https://betterstack.com/logs)