Adds scala-steward badge

Author: albertpastrana

README.md

@@ -2,5 +2,6 @@
 
 [![build](https://github.com/intenthq/scala-secret/workflows/build/badge.svg)](https://github.com/intenthq/scala-secret/actions?query=workflow%3Abuild)
 [![Latest version](https://img.shields.io/github/v/release/intenthq/scala-secret?include_prereleases&sort=semver)](https://github.com/intenthq/scala-secret/releases)
+[![scala-steward](https://github.com/intenthq/scala-secret/workflows/scala-steward/badge.svg)](https://github.com/intenthq/scala-secret/actions?query=workflow%3Ascala-steward)
 
 A tiny micro-library with a wrapper for secret values that prevents them being printed by accident anywhere.