Update README.md

Author: j5ik2o

README.md

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 # docker-controller-scala
 
 [![Scala CI](https://github.com/j5ik2o/docker-controller-scala/actions/workflows/ci.yml/badge.svg?branch=main)](https://github.com/j5ik2o/docker-controller-scala/actions/workflows/ci.yml)
+[![Scala Steward badge](https://img.shields.io/badge/Scala_Steward-helping-blue.svg?style=flat&logo=data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAA4AAAAQCAMAAAARSr4IAAAAVFBMVEUAAACHjojlOy5NWlrKzcYRKjGFjIbp293YycuLa3pYY2LSqql4f3pCUFTgSjNodYRmcXUsPD/NTTbjRS+2jomhgnzNc223cGvZS0HaSD0XLjbaSjElhIr+AAAAAXRSTlMAQObYZgAAAHlJREFUCNdNyosOwyAIhWHAQS1Vt7a77/3fcxxdmv0xwmckutAR1nkm4ggbyEcg/wWmlGLDAA3oL50xi6fk5ffZ3E2E3QfZDCcCN2YtbEWZt+Drc6u6rlqv7Uk0LdKqqr5rk2UCRXOk0vmQKGfc94nOJyQjouF9H/wCc9gECEYfONoAAAAASUVORK5CYII=)](https://scala-steward.org)
 [![Mergify Status](https://img.shields.io/endpoint.svg?url=https://gh.mergify.io/badges/j5ik2o/docker-controller-scala&style=flat)](https://mergify.io)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.github.j5ik2o/docker-controller-scala-core_2.13/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.github.j5ik2o/docker-controller-scala-core_2.13)
 [![License](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)