doc: add OpenSSF scorecard

#4172

Author: JakobLichterfeld

README.md

@@ -1,5 +1,6 @@
 # TeslaMate
 
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/10859/badge)](https://www.bestpractices.dev/projects/10859)
 [![CI](https://github.com/teslamate-org/teslamate/actions/workflows/devops.yml/badge.svg)](https://github.com/teslamate-org/teslamate/actions/workflows/devops.yml)
 [![Publish Docker images](https://github.com/teslamate-org/teslamate/actions/workflows/buildx.yml/badge.svg)](https://github.com/teslamate-org/teslamate/actions/workflows/buildx.yml)
 [![Coverage](https://coveralls.io/repos/github/teslamate-org/teslamate/badge.svg?branch=main)](https://coveralls.io/github/teslamate-org/teslamate?branch=main)