add readme dependabot badge

Author: stronk-dev

README.md

@@ -4,6 +4,7 @@
 [![NPM](https://img.shields.io/npm/dy/@stronk-tech/react-librespot-controller)](https://www.npmjs.com/package/@stronk-tech/react-librespot-controller)
 [![NPM](https://img.shields.io/bundlephobia/min/@stronk-tech/react-librespot-controller)](https://www.npmjs.com/package/@stronk-tech/react-librespot-controller)
 [![GitHub License](https://img.shields.io/github/license/stronk-dev/react-librespot-controller)](https://github.com/stronk-dev/react-librespot-controller/blob/master/LICENSE)
+[![Dependabot Updates](https://github.com/stronk-dev/react-librespot-controller/actions/workflows/dependabot/dependabot-updates/badge.svg)](https://github.com/stronk-dev/react-librespot-controller/actions/workflows/dependabot/dependabot-updates)
 
 > [`go-librespot`](https://github.com/devgianlu/go-librespot) squeezebox-alike web frontend for small touchscreens