chore: add openssf scorecard badge

Author: naltatis

README.md

@@ -1,5 +1,7 @@
 # evcc Companion App
 
+[![OpenSSF Scorecard](https://api.scorecard.dev/projects/github.com/evcc-io/app/badge)](https://scorecard.dev/viewer/?uri=github.com/evcc-io/app)
+
 Native app wrapper for evcc UI based on [react-native](https://reactnative.dev/) and [expo.dev](https://expo.dev/). It uses [UI Kitten / Eva](https://akveo.github.io/react-native-ui-kitten/) as a design system. Native parts are written in TypeScript and kept to a minimum.
 
 ## Download the App