Update readme with kotlin version

Author: xxfast

README.md

@@ -9,7 +9,7 @@
 
 [![Kotlin Alpha](https://kotl.in/badges/alpha.svg)](https://kotlinlang.org/docs/components-stability.html)
 [![Build](https://github.com/xxfast/Decompose-Router/actions/workflows/build.yml/badge.svg)](https://github.com/xxfast/Decompose-Router/actions/workflows/build.yml)
-[![Kotlin](https://img.shields.io/badge/Kotlin-2.0.20-blue.svg?style=flat&logo=kotlin)](https://kotlinlang.org)
+[![Kotlin](https://img.shields.io/badge/Kotlin-2.1.20-blue.svg?style=flat&logo=kotlin)](https://kotlinlang.org)
 [![Maven Central](https://img.shields.io/maven-central/v/io.github.xxfast/decompose-router?color=blue)](https://search.maven.org/search?q=g:io.github.xxfast)
 
 ![badge-android](http://img.shields.io/badge/platform-android-6EDB8D.svg?style=flat)